Definetly get GTA 4, it a state of the art game and should not be passed up.
If ya looking for a good fighting game I recommend Mortal Kombat vs DC Universe or UFC 2009 Undisputed.
If ya looking for a fun smash em up I recommend Prototype or Ninja Gaiden Sigma.
If its a racing game ya looking for then GRID is awsome!
Or if ya into the RPG based games then I recommend Elder Scrolls: Oblivion, Eternal Sonata, FallOut 3 or Folklore.
If ya into fun violent games then I recommend GTA 4 (lol), DeadSpace, Silent Hill Homecoming and Condemned 2.
If ya into to scary dark games then once again Condemned 2 or Silent Hill or Resident Evil 5.
If you like shooters the Resistance 2, Fracture, Kill Zone 2, Haze and Red Faction Guerilla are GREAT! Hope I helped