Welcome to the world of the Turbo
I just got a Duo a few months ago, here's what I'm enjoying:
HuCard-
Neutopia - an easy Zelda clone, with more emphasis on fighting and less on puzzles...
Blazing Lazers - an intense shooter with awesome graphics and music for the time
Somer Assault - a strange game where you control a Slinky like creature... not for everybody, but certainly unique
Bonk series - side scrolling platformers with fairly stiff controls... I'm not as big a fan as everyone else is though
CD (US)
Exile - short but easy side scrolling RPG in an Arabic setting during the Crusades. Interesting, although slightly out of place soundtrack (I didn't know they listened to 1990's sounding house music during the Crusades!), and the game is really short and easy
Ys Book 1 and 2 - even though the combat system is odd (run into enemies to attack), it sounds better when you're actually playing the game, than it does on paper. The music is one of the classic game soundtracks, and the level design is incredible... There are lots of items, cool puzzles, and the like. If I actually got a chance to play this game in 1990, when it first came out in the US, I would've been blown away.
Ys 3 - I didn't like this one... I own the SNES and the CD-ROM2 versions.. The CD-ROM2 version has some of the choppiest scrolling you'll ever see, and both games have grainy graphics. The music is excellent, once again.
Gate of Thunder - A horizontal shooter with some awesome power-metal music, cool powerups, and gorgeous graphics that look better than most Genesis and SNES games.
Shadow of the Beast - Got this game with the system... it's one of the worst games ever made, you can actually get stuck (in lots of points) and are forced to reset the game... The monster design is really silly and unique, I have to give them credit for that. Interestingly enough, it's made by DMA Design, now known as Rockstar North... yes, the GTA people.
Cosmic Fantasy 2 - I heard this is a great oldskool RPG
CD (JP)
Ys 4 - haven't played much of this, but it looks to continue the amazingness in Ys Book 1 and 2
Dracula X - the forerunner to Symphony of the Night... plays more like Castlevania 3 than SOTN, but many of the enemies will look familiar to SOTN fans. The graphics are some of the absolute best on the system, some of the special effects are mindboggling, the music is excellent (a lot of it is remixed songs from CV1-3), there's 2 different routes through the game, some secret stuff to find... It's a bit easier than the NES CV games, and it has a save feature which is very nice. I'm like 76% complete with it currently... It costs a lot but it's definitely worth it.
Tengai Makyo 2 - a classic RPG with amazing cutscenes, good music, and attractive graphics. Supposed to be long as hell too. Plus it's got a good sense of humor (like all the Tengai Makyo games). A US release was supposed to happen but got scrapped
