I have enough money for 1 game, but I dunno which to get? Help

I just got my first pay check at DQ =D and I have enough money to 1 game for PS3. I was wondering which game to get or save it for future game that is coming up.

I have:

CoD:WaW

Killzone 2

Rainbow Six Vegas 2

Warhawk

Little Big Planet

MGS4

GTA IV

Resistance 2

I prefer FPS games and online games. But I can try some of your favorite games. If there are really great game that is about to be released in the future, list them also. Thx for your help. (I also except old games on the PS3) Great games never get old.

street fighter 4 or CoD4. in my personal opinion, CoD4 is better than WaW.

it depends on what you are looking for, if you have online support or if you prefer single player games. if you like longevity or quick fun

for online, Killzone or GTAIV or Street fighter 4

for single player, killzone or GTAIV, i Reccomend fallout three

For longevity, GTAIV

Quick fun, Little big planet, street fighter 4