I've been playing King of Fighters 2002: Unlimited Match lately. It's not quite the Smash Bros. Ultimate of KOF (that would probably be '98 Ultimate Match; 2002 is missing some characters who appeared in KOF before like Wolfgang Krauser), but it's got a very big roster (66 characters counting alternate versions).
I played through Endless Mode (the game's record feature helped - it made it so I could map Rugal's Kaiser Wave to a single button press), unlocking Igniz, Geese, and Goenitz in one fell swoop. (I didn't even know Goenitz was in this game!)
Also, I've been playing a bit of Mortal Kombat vs. DC Universe. The game feels kind of sluggish, and using special moves seems inconsistent. (it feels like half the time I try to use a special, it uses a regular attack instead) Still, I'll give it a chance - it turns out that I didn't beat the story modes for that game, so I'll try to do that, at least.
On a related note, Capcom Fighting Collection 2 comes out in less than a week. Out of the games in that collection, I've only played Capcom vs. SNK 2, but that game alone makes the collection worth it, and I'm looking forward to trying out the other games. (even Capcom Fighting Evolution)