Agreeing with the previous posters. Your system is not powerful enough to run the game on max settings (or any of the other games you listed).
yes he can play the other games at maximum settings on the resolution of 1400x900...
mw is nothing to gpu, i think i can max out mw3 with my old 9800gtx+, about crysis 2 i could max it out (Without dx11 patches/HD texture packs) with my 560 ti and a e8400 cpu at 1080p so i think that he can max out at 1400x900. just GTA 4 will not be able to run maxed even at low resolution because of the problems already related.