I've got a little bit of time to kill, so I'll jump in at the behest of laughingbanana.
I'm going to stick with native Vita games that are on my trophy list. This may mean there are games I have (from PS+) that I never bothered to download and play because I had no interest or didn't like them. Hell, some of the games in this list were 1 session and delete because I thought they were terrible.
Assassin's Creed III Liberation* -- Solid. Really felt like AC in my hands. Some framerate issues, but not enough to ruin the game. Some bugs, too, but most of the catastrophic ones were patched out before I played. Multiplayer was a terrible terrible idea and a waste of time.
Atelier Totori Plus -- Only played for a little bit but seems to be a worthwhile JRPG. The graphics were nice and the combat seemed enjoyable. The voice acting seemed terrible and I'm unsure about the alchemy/item crafting mechanic, but for now I look forward to going back when I want to play a JRPG.
Big Sky Infinity -- I was disappointed by this... there are sections where it's hard to tell how or why you died. The powerups you work toward getting never feel like they're doing anything... The music and some of the graphics are kind of cool, but there's nothing special here.
Blazblue: Continuum Shift Extend -- Wonderful port of the console version. Works well on Vita because it's a 4 button fighter (mostly). Graphics are wonderful, everything is fluid, 60fps.
Chronovolt -- Terrible. An insult of a PS+ title.
Dead or Alive 5 Plus -- Can't really comment as I haven't actually played any yet... normally I don't like DoA games, but hey... $10 for a well done port and my Vita has a lack of 3D fighters anyway...
DJMAX Technica Tune -- Seemed well done... I found even the early stuff to be challenging as I suck at these kinds of games. Music selection seemed diverse even though I wasn't familiar with most of it. The variety was nice as I was able to find a few songs that were even close to something I'd listen to normally and it wasn't all just J-Pop or whatever.
Dokuro* -- charming and fun puzzle platformer. It was a steal at $10. It was criminal to pass it over when it was less than that... and free on PS+? Shame I already owned it. Sometimes it's a little slow and you NEED to switch the change setting to use buttons instead of touch... but it was very cute and entertaining.
Dragon's Crown -- Don't know, haven't played yet, waiting for news on the new patch that's live in Japan being released here first.
escapeVektor -- reminds me a little of Pac-Man. Starts out really slow... you need to get your FW level up before you judge the game. Really challenging really quickly.
Escape Plan -- this was a solid title. some of the controls were a little wonky, but since the patch came out, it's much better or so I'm told. I enjoyed it for a runthrough but not enough to buy the DLC.
Flying Hamster HD -- Reminds me a little of Parodius... it's a cute little shmup but nothing that will satisfy your shmup cravings... definitely worth the $4 or so though, if you like shmups.
Foosball 2012 -- Another terrible PS+ game.
Frobisher Says -- This was fun. I liked it enough to buy the DLC packs. Some of the AR camera stuff is wonky and frustrating... but you can turn a lot of those games off now. It's like Wario Ware, I think? Definitely worth checking out for the price of FREE.
Germinator -- Seemed okay but not really my cup of tea.
Gravity Rush -- A wonderful exclusive. The DLC is worth it if you get it from the start, I think. This is another game where it starts out slow and you need to level up before you can really enjoy it. I'm hoping for a sequel.
Guacamelee! -- one of the best metroidvania games ever. great sense of humour. surprisingly deep combat and challenging platform sections. check out the DLC if you're grabbing this and haven't played it.
Hotline Miami -- FANTASTIC on vita. I played it on PC and thought "I just want to finish this game, I'm getting frustrated now!". Then I bought it on Vita and played it with some headphones... Changed my mind completely... went from "kind of overated indie game" to "holy crap in a pita everyone needs to own this if they own a Vita".
Hot Shots Golf: World Invitational -- seems solid. people rave about it. it didn't really click for me before I needed space on my memory card, so it's in space crucnh limbo hell right now. If I ever get a bigger card, I'll bring it back and try again.
Jacob Jones -- solid Layton like puzzle game. If you're a trophy minded person, beware of the stupid "find all the soda cans" trophy. That was annoying. Other than that, it was really good and I was/am looking forward to the next chapter, should it be made.
Jetpack Joyride -- not a bad game once they patched in button controls. especially not for free. seems like the standard "runner" type iOS/android game though.
Jet Set Radio -- I never played this on Dreamcast, so I have no nostalgia factor. I wanted to like it, but it's one of those games that's difficult because the controls suck. I couldn't get into it... thankfully it was a free PS+ game.
Limbo -- don't know, haven't played it. I will go through it soon.
LittleBigPlanet Vita -- FANTASTiC. Should have been LBP3. Best game in the series, by far. It takes everything you know about LBP and refines it into one hell of a portable console experience.
Lumines -- Great puzzle/music game. I'm not good at it so I haven't become addicted... also, I'm not huge on the music genres used in it, so I'm not as gung-ho as everyone else, but it's an amazing title.
Men's Room Mayhem -- At first I liked it... seemed solid. Then the trophy hunter in me showed up and I ended up trying the "challenges". This became infuriating to the point where I wanted to throw my Vita. The game was deleted as I felt like it was just impossible. I do NOT recommend paying money for this.
Mortal Kombat -- Fantastic port. 60fps, all console ontent and then some. Online worked well when I tried it. Biggest knock people put on it is the lower poly models and low quality textures... but that's hard to notice at 60fps so it's only really a problem in the pre/post match stuff and even then, I don't really care about it myself.
Motorstorm RC -- Took awhile to grow on me, but it's a fantastic game. Reminds me of RC Pro-am and Offroad from my childhood days. Definitely worthwile, the DLC is worthwhile too; just get the full pack.
Muramasa Rebirth -- ABSOLUTELY STUNNING VISUALS (see the screens I posted). Combat is a little bare for an "action game" since everything revolves around [] button. This leads to some imprecise actions too, which can be frustrating. It can get boring running from A to B sometimes, those are valid complaints I've seen about this game. Overall a great title though, even with the knocks I have on the new translation style.
Ninja Gaiden Sigma+ -- The drop to 30fps (and even then, the slowdown at parts) make this hard to recommend. It's solid, but I'm glad I got it for free. Especially with some of the bow aiming touch screen stuff.
Nun Attack -- Fun little iOS game. I liked it enough to just about perfect everything and get 100% of the trophies.
Oddworld Stranger's Wrath -- Solid port. Fun game for the most part. Gets REALLY boring toward the end and you end up usin the same 2 or 3 weapons... but the 1st half of the game was wonderful.
Persona 4 Golden -- FANTASTIC. The hype doesn't lie. If you like JRPGs, you'll probably like this game.
Plants Vs. Zombies -- PS+.. played the hell out of it on 360/PC, so I never felt compelled to boot it on Vita.
Playstation All-Stars Battle Royale -- it's an okay game. It's better with friends... the cross-play is nice. Single player it gets boring quick. I like it better than Smash Bros. for sure. I wish it had some better PS characters though.
Pure Chess -- seems like a good chess game, pretty graphics, asynch play. nobody on my list that's played a game with me has had the attention span to finish, so I deleted it for space.
Rayman Origins -- My favorite classic mario-style platformer of the past 15 years... just amazing. I loved the game on PS3, so I bought and played it again on Vita. I wasn't disappointed.
Resistance: Burning Skies -- Average overall, but a good fix for an FPS proof of concept on Vita. I think it gets more hate than it deserves. Very easy platinum, if you care about that sort of thing.
Retro City Rampage -- Terrible. Abomination. PS+ is apparently run by sadists.
Rocketbirds -- This is a mixed bag. I really liked part of it. If I wasn't a trophy hunter, I'd probably have liked it more. Between the busted online, collecting the flags, and some other issues, I was left with a bad taste in my mouth, so to speak. But a decent game overall.
Silent Hill: Book of Memories -- Better than people make it out to be. But I can't imagine it without the patch or DLC. I wish the online worked better.
Sine Mora -- Fantastic. This game is in the same realm as Rayman Origins for me. I love it -- everything about it -- and so I bought it on Vita and I wasn't disappointed. The only knock is that in some of the later stages, you can run into some slowdown and it's a bit jarring considering most of the game runs at 60fps.
Sly Cooper 4 -- Impressive port. Solid experience. Recommend getting the PS3 version for cross-save so if you hit some of the framerate/draw distance issue areas you can just switch to ps3 for a bit and switch back.
Smart As... -- A good Brain Age knock off, but it can get old/boring kind of quickly.
Soul Sacrifice -- Spectacular. I've never liked a hunting game before (I bought MHFU on PSP thinking I might) and while I don't like comparing the two, this one is leaps and bounds above Monster Hunter for me. The art direction, sound, combat... everything is amazing. There's a lot of variety and spell crafting... there's grinding if that's your thing, etc. Online plays pretty flawlessly and it's been supported by a metric ton of good/free DLC. Highly recommended.
Sound Shapes -- A disappointment for me. I love Jonathan Mak and Quesy Games... I loved Everyday Shooter and this was one of the main reasons I wanted a Vita (back when it was exclusive and not cross-buy). However, I wasn't into the level creator, death mode is terrible, and the main levels end up being too easy and short. Some of the community levels were well done, but I gave up on it and deleted it after I got my platinum to save space.
Spelunky -- fantastic and frustrating at the same time. I both love and hate this game. The cheap deaths it throws at me lately have me raging, but I'm compelled to get better at it so I can be like Esoteric!
Stardrone Extreme -- Was this PS+? Or did I just buy it because it was $2? Either way, I wasn't impressed. I didn't like the controls. Deleted.
Stealth Inc. -- Fanastic. I stopped playing because of other games, but the game looks great and plays great on Vita. My only knocks were that NA didn't get the DLC levels for free and there's no real reason to replay the levels to unlock the upgraded clones for use.
SFxT -- wonderful port, but suffers a bit from the "how do I play a 6 button fighter on a pad". I've had that issue with SF games since SF2 on the SNES... so I've always been a fightstick guy and it's hard to play for me. I end up neglecting some buttons which is terrible in this game because you have things like tag and whatever mapped to dual button presses. PS3 owners tend to discriminate against Vita owners if you try cross-play.
Sunflowers -- iOS game. Bought it to support Atelier. Still better than RCR, which released the same week. Got bored of it quickly, deleted.
Super Stardust Delta -- fantastic. everything you could want in a portable Super Stardust. I like the modes where you can get rid of the gimmicks and even better, I liked how they let you remap touch gimmicks to buttons in the options.
Tales from Space: Mutant Blobs Attack -- Drinkbox delivers again. After playing this, I went and bought the PS3 game, but haven't really put any time into it yet. A charming little platformer with some nice replay value if you're up for going for gold on every level. Loved it so much I bought it on Steam when it came out there. Loved it enough to buy it for friends so they would play it.
Touch My Katamari -- Quality katamari on your handheld. People knock the DLC, but you don't have to pay for it, just grind a little if you want it. Overall, it's a solid game and worth the $3.75 it was going for on sale a few weeks back.
Treasures of Montezuma Blitz -- After the trophy patch update, this was a regular daily game for me. I loved playing it and trying to get high scores... good leaderboard implementation too. I ended up getting bored of it though and wasn't willing to grind another 70 hours for the last trophy.
UMvC3 -- fantastic (I use that work a lot here... Vita must have some fantastic games, i guess). port of the console version. Works better than SFxt because you can put the assists on the shoulders and then it's only a bit challenging to do snapbacks instead of doing your core special moves. Online was kind of dead when I last played. Wish it had cross-play with console.
Uncharted: Golden Abyss -- Impressive bit of technology. I never want to play a console Uncharted again because I'll miss the "touch to climb" stuff. That was a god send. The aiming takes some time to get used to, but a good effort overall and impressive for a launch title. 3rd best game in the series for me.
Unit 13 -- great game if you like TPS. Bite-sized missions... interesting level up mechanic and character variety. It was fun 5-staring everything. Co-op is supposed to work well, though I didn't really use it.
Urban Trial Freestyle -- Seems like a fun Trials type game. Sometimes the controls/physics are extra wonky, but it's fun and overall pretty well done. Small file size and reasonable price are also bonuses.
Velocity Ultra -- solid game concept. I ran into a lot of bugs and the controls were terrible in spots. Don't look here if you're looking for a shmup though, it's not really like that.
WipEout 2048 -- amazing visuals. felt great when I was playing it regularly... I'm not a huge racing game guy but I keep this on my card. Load times were kind of bad, but worth it. DLC from owning HD and Fury was also outstanding and added a lot.
Zen Pinball 2 -- Seems like a solid pinball game. I like the "arcade" feel here, as I don't want a pinball simulator... then again, I had a lot of fun with metroid pinball and sonic spinball... so yeah. Haven't tried the star wars tables, but the PvZ table was my favorite.