If you told me I could only play one video game for the rest of my life my response would be "Dude, why you being such a dick?" After you explained yourself and made it clear I had no choice I would say Marvel Versus Capcom 2. Or, that would have been my answer for the last 10 years. It looks like my new choice might be Marvel Versus Capcom 3.
I'm not saying MVC2 is the best game ever, nor is it the best fighting game ever, but it is my favorite. Other fighting games can boast three dimensions, fatalities, and bouncing boobies. MVC2 is just super fast 2-D action that offers over 50 characters from Marvel comics and Capcom games.
(Yes, Wolverine is in there twice. He's that awesome.)
We used to play this game all the time in college. Seriously, as much as possible. The game is not without its flaws, namely the awful repetitive music. But you just mute that, crank the WinAmp (yep, that), and you can play for hours. But the great thing about this game is I keep going back to it. When it became DLC for PS3 I yoinked that shit right up. It's just that much of a classic. I am a huge fan of this game.
(OK, not that big of a fan)
Well needless to say I am psyched about MVC3. There are going to be a lot more characters, but hopefully they keep the frantic speed and tag team controls. Here is the teaser trailer for your viewing pleasure: