Your lack of Blazblue in the poll disturbs me. And SFxT doesn't come out till september, so you got plenty of time to save up for that.
UMvC3 is great, and little to no compromise between the conversion from console to portable.
MK took a rather big hit on the visuals, but it has all the content and then some from the console version.
Blazblue is still my fighter of choice, and looks exactly like the console version. Really good online, and just overall awesome and my most played game on the Vita. Has a solid community on it too.
And if you are looking for a platformer, look no futher than Rayman Origins. It is beautiful, plays great, and just overall fun. The vita version doesn't have the online co-op, but the game plays fine without it.
So yea...Blazblue and Rayman are must haves in my book.
I will also shamelessly promote Dissidia as well if you don't already have it. One of the best PSP games ever, and just one of the most fun and unique fighters to come out in a long while.