THE Capcom and SNK crossover game. You can ignore the rest if you want.
What crossover games need is a special feeling. The prequel to this game somewhat managed to capture that, but some fine tuning could have gone a long way. Capcom vs SNK 2 managed to do that fine tuning.
The stages mostly feel special, but I will admit there are only a few of them here. I could have used more stages, personally. Get rid of the one with the windmills and New York, those are lame. The roster got some additions to make this feel a bit more like Capcom vs SNK instead of Street Fighter vs King of Fighters.
More importantly, the Groove system added some depth and it's mostly appreciated, barring a few grooves that can be unbalanced (A, K). On top of that, you can actually choose how to spread the Ratio among your characters. Major game changer right there. There's also a 3-on-3 mode if you don't want to bother with the Ratio system.
With the large cast of characters, the teams you can make, the way you can make the same teams play...there's just so much replayability right there. Plus, you can get different boss battles depending on the Groove Points you get during your playthroughs. Due to this, you can get better endings to this game than in the prequel, where you basically had two that looked poor.
There are also unlockable modes and you can get Shin Akuma as well as God Ultimate Rugal.
On top of that, the soundtrack is a vast improvement over the previous game, if you ask me. "This is true love we're making" pretty much kills the CvS soundtrack by itself, sorry, I don't make the rules.
The PS2 port holds up its end of the deal well enough, we're not talking about some weak PS1 port here. Playing this with a Dualshock 2 controller is a great experience.
Graphically, the 2D sprites are top notch. As I said, I'm not really behind mixing that with 3D stages, but most of them look good enough. The music's good or even great, and there's enough reasons to keep playing. Okay, maybe they could have taken the Marvel Vs. Capcom 2 approach of having more characters to unlock, but that just depends on how you look at it. I like having almost everyone available from the beginning, so there you go.