I'm gonna join this discussion.
I've only played the PSP versions (MHF, MHF2, MHFU) and MHF was awesome, MHF2 was less fun, MHFU was a bit redeeming but still marginal upgrade from MHF2.
Going back to MHF now feels really archaic. MHF2 however was way too easy (everything is handed to you for free and high end armor had way too much defense). MHFU continued this lack of challenge but at least provided some neat monsters.
MHF2 was the worst upgrade in my opinion, adding crabs (!?) and farting monkeys (!?!?). I know they're trying to expand the definition of "monster" but adding stuff like that will reduce the quests' quality. Monster Hunter is about epic battles. not joke monsters.
As for every weapon that has been added since the original:
Dual Swords never felt interesting to me. It's hardly ever used as a base weapon
without mega juice. Spam fest weapon. I'm strictly against weapons requiring mega juice. I don't use it for my lance (unlimited blocking, hoppping and running) or my hammer (unlimited charge holding and rolling), so I don't use it for DS either. MHFU at least made it a bit interesting by adding dual elements, but it was still a
spamfest.
Bow. At first I had fun with it but after some playtime you'll start to realize this weapon is strongest at a specific range with a specific charge. So you keep shooting the same shot from the same spot over and over again. This basically means the most effective way to fight is the most boring one. Fun if you don't know what you're doing, totally boring if you know what you're doing. Unlike other weapons which depends on milliseconds timing when you try to improve, this one just needs repetitions and hardly any insight. I'm not missing it and it also made the gunner sets confusing because some gunner skills had a double meaning.
Gunlance. After seeing a prototype gunlance in MHF1 (basically a lance with fire damage) and then using one in MHF2 was totally awesome. This weapon has advantages and disadvantages. The wyvern fire looks kickass (but is actually kind of weak..., equals 4 shots). I wouldn't mind seeing this weapon soon.
Hunting Horn. Using this weapon during solo play is a pain. It doesn't have many ways to attack, so the only plus about this weapon is the horn play. Which is a trade-off that's totally worth it. A team with multiple hunting horn players give such a great sense of teamwork. It does however remove a bit of the "300 (the movie) soldier" feel, because the HH players needs to do some buffing every few minutes, being a bit of a slave for the team.
Long Sword. Interesting weapon with some limited movement (mostly forward). Though it's not my personal fav because of how it broke most of the weapon balancing in teams. The weapon itself and how it's balanced is fine, but in teams that weapon is still the most ridiculous teammate hitter. It slashes everywhere and the LS user gets hit immunity while attacking. Fortunately Tri offered the LS late in the game, so people at least play with other weapons first. In MHF2 and MHFU I had to deal with people who never used any other weapon and doesn't realize how damn annoying it is to get hit by a LS every few seconds. Oh ya, thanks for hitting me before I finish my triple pound. Oh, thanks for return slashing yourself to safety and tripping me INTO Khezu's Blanka move.
To me MHF2 offered some interesting weapons, but a lot of unbalanced things and uninteresting things as well. It made the quality of the series a bit less to me. Worst offender being that armors can be upgraded so much that you're allowed to play shitty to survive. Most monsters aren't interesting except for Rajang and Tigrex.
MHFU redeemed itself with one of the cutest monsters: Naruga. It's design should be more unique (looks a bit Tigrex-like) but it's movement is quite unique, so it's fun. The slight changes in the system were all pretty small, so for people who jump from MHF2 to MHFU it's quite a steep price for more of the same gameplay.
I have at least logged 500 hours in each game (more unlogged, like unsaved data), probably exceeding 2000 hours in total before I started Tri.
Tri offers so many new things, it feels as if I'm playing MHF1 again. With MHF2 and MHFU I felt like I was playing catchup: just trying to get to G-rank ASAP and that's it. A reboot was a smart choice and I'm thoroughly enjoying the new monsters. It's good that I read nothing about the monsters, so every encounter was pretty amazing. The rebooted monsters feel much more natural and it seems to make sense now how they move and attack. I agree with Luigiv that they're closer to being build from the ground up than having just a few new attacks. Even if attacks look the same (Diablos), it definitely moves different and the safezones and hitzones are different (and this is not just an engine thing, but clearly redone).
Tri offers some very interesting weapon changes which emphasizes the weapon types.
Sword n Shield's shield bash offers versatility, Hammer's unlimited combo showcases raw close range power, Great Sword's 2nd charge form to truly test your timing and prediction skills, Bowgun parts to satisfy your love for planning and preparation, Long Sword's power up for continuous fearless offense, Lance's counter to conquer the world without budging.
Switchaxe has almost the same level of complexity as Gunlance, which is great. It's very flexible too, as you can fight in a permanent sword state (instant sword mode unleash) or in a permanent axe state, or switch around if you like that. All up to the player. It's a very nice addition to the MH weapon set and definitely way better than the DS or Bow ever were.
Tri offers so much new stuff that even I can enjoy it right from the start. MHF2 and MHFU probably has more content for a new person to the series, but to me Tri offers way more and I personally think the quality is higher overall. I'm definitely satisfied (still playing, mind you!) with what I'm playing. However, I also wouldn't mind if there's going to be a Tri G. I'm currently in high rank and can see the end coming near. I'll probably get about 400 hours out of this game before I stop, so I won't feel ripped off in any way. But if they add the same quality of new content as a G upgrade as they did with this Tri reboot, I'll gladly buy that on day 1 as well. What I don't like to see is the return of Khezu, Plesioth, Gypceros. Lao Shen Lung, Akantor and whatever those crabs are called. Those monsters don't add anything anymore and especially in Tri, there are much cooler variations of those types (Giginox and Lagiacrus).
