Since most fighting games are total garbage, I'd have to say Def Jam: fight for new york. I liked vendetta more, but FfNY is hilariously bad. And by bad, I mean LOLWUT. I beat the game's story mode 3 times, and versus mode just comes down to timing.
I've had more fun with that game than SSB, because this game is so fucking silly with the insults and with the total fake hip-hop world.
Virtua Fighter is my favorite competitive fighting game, because that game got to the point where I needed to practice (A LOT) to be skilled. I'm glad that it's for people who actually enjoy fighting games and isn't a button mash. It is way more satisfying than any other fighting game I've ever played (killer instinct (though that took time too), tekken, street fighter (I was a young piece of shit), Soul calibur (though I love that one...), etc...)
But anyway, Def Jam FfNY lets you throw people in front of a subway, smash their car with their body, dish out a combo called "NY Nightcap" where you hit someone over the head with a golf-club, has a lot of blood, an interesting fighting system with several fighting styles, (leaving the game as a street-fighting game with wrestling-heavy elements) and several other things that set it apart from other fighting games. The story mode is sorta cool, and the generic underground-style drama happens...and people leave you threatening voicemails, which are a big source of laughs.
As I said, the game is terrible, but it's so much fun. It's one of those fighting games I can turn on, play for 20 minutes, say "hahaha, oh wow" and go do something more worthwhile with my time.
Killer Instinct Gold is a classic one for me, as is Bloody Roar Primal Fury, and VF is my personal "best" but not favorite. ^^;