All of em.
Free Step Dodge
Project Bokuho
All of them.
UpSideDownGRUNT
whichever series you prefer most 
butItotallyreccomend5U
butItotallyreccomend5U
Chaos
I can only afford one game right now....T_T
Brute
Then 5U
SilverForte
5U then, doa needs all the support it can get.
Chaos
5 stages, no classic throwback for Ryu and characters getting nerf?! Naw I'm good haha just kidding ^_^ lol
haha just kidding ^_^ lol
UpSideDownGRUNT
with anyluck they'll atleast put the NGS2+ version in 5U even if it's DLC
Rubedood
VF
WiZzYx
VF5: FS all the way.
XxSakuraLuvaxX
5U! :3
Awesmic
Whichever one has Hitomi on the cover. If you manage to find one with Hitomi Tanaka on the cover though, you're in for a real treat.
duh