One of the best fighting games of all time- hands down.
But OK, it plays like your typical hardcore 2D fighter, but the catch is that you can call your teammates (up to 3) to assist you. Of course, you can also change places with them and let the other character replenish health.
That's pretty much all there is to it, but it doesn't get old.
As for the Single Player modes, there are pretty much a lot, and all of them (even Versus matches) give you points based on performance. These points you use in the store which houses all the unlockables: characters, colors, etc.- which after every purchase, will increase in cost- therefore making you want to play more and more and more.
Well, there are definitely a lot of unlockables, therefore you are guaranteed to spend months collecting points just to complete everything. So yes, not only is it a really fun game, it's also a really good buy. I recommend this to anyone who loves Marvel and Capcom, and want to see a match-up between these heroes. And frankly, what with the HUGE HUGE HUGE character roster, these match-ups have almost limitless possibilities.
Plus, you'll also spend time fine-tuning your combos because of its expansive command list, and you'll also want to experiment with several characters their united superpowers (or in simpler words, the supers of all three combined) to see how much damage, and number of combos you can rack up. It's really addicting to experiment with that, and it's really fun to execute them as well.
Overall, I really, really love Marvel vs. Capcom 2 to death. It's definitively one of the greatest fighting games in the history of mankind... BUY IT! You won't be disappointed!