Gotta go SS2, just for amount of time I've spent playing it with friends.
MotW is just god like, but I enjoy RB2 for some fun.
KoF97 is my goto, the music in 98 does nothing for me. After that, I sort of can't tell the differences since I'm not hard core KoF fan. XIII is the best thing SNK could have done with the series; brought it back in HD keeping hand drawn sprites. I hope they can do that for other IP's they still have.
Ninja Masters is good fun that most ppl missed in the arcade. NeoGeoX should have put it back on everyone's radar. It's like a lost SF2 from BitD.