SF2 vs SFIII is really a matter of preference I find.
Street Fighter III: Third Strike is considered almost universally by fighting game fans to be one of the finest fighters ever made, but at the same time there are a lot of aspects that mean people don't like it as much as SFII or other fighting games.
Main issues are:
Parry System: On paper a great idea, and one of the most loved aspects of the game, but also one of the most hated. Critics argue that it destroys zoning (fireballs) almost entirely, or that it creates a 'Guess and Win' meta-game where a single parry can turn the match. It also nullifies things like anti-airs sometimes with air-parries.
Unbalanced Roster: While Kuroda, the best 3S player in the world most likely, can beat people with low tier characters, almost every tournament for this game ever is Chun Li vs Chun Li. Sometimes you'll see Yun being used and even more rarely, Makoto. The game is terribly balanced and Chun Li just overshadows the entire cast.
Street Fighter 2 on the other hand, peaked in most people's eyes at Super Street Fighter II: Turbo (although many do enjoy Street Fighter 2: Hyper Fighting, and some even still prefer Champion's Edition). This game is really well respected for it's simplicity and emphasis on fundamentals. It too has problems though;
Balance and Counter-Picks: This game is also really unbalanced, but unlike Street Fighter III, it's all around counter picks. Characters have very lopsided match-ups and it can sometimes become a game of Scissors, Paper, Rock sometimes. Not to mention Old Sagat is almost bannable he's so good.
Technical things: The game has random damage output for some moves, and I believe the game skips frames of animation due to the turbo setting which can throw off things like reversal timing.
Overall, I think you'd be mad to dismiss either game for their quality, they are two of the most respected and important fighting games around. In terms of financial success, almost certainly SFII was more popular, I think SFIII was actually relatively unpopular at the time.
Marvel 2 was Capcom playing with MUGEN.
What were we talking about again? I think it was something to do with revisions of capcom games, basically I like it. I like seeing revisions to fighting games, they can always be improved. If they aren't people will usually go back to an older version or it'll get fixed again. I would love a KOFXIII Ultimate Match for example...