I have a core 2 duo (2.80ghz) processor, 3 gb Ram, 32 bit machine, plz suggest me a graphics card... I want to play call of duty black ops 1, gta v, watch dog ....e.t.c
GTA V has not been released on PC yet, with no release date announced just yet. The full watchdogs requirements are not published yet, but it looks like it will require 6GB of ram and a 64 bit OS.
Im sorry to say, but it looks like you will need to upgrade the rest of your computer if you wish to play these new release 'next gen' games. there is no real point sinking a large amount into a graphics card, only to have it bottlenecked by the rest of this system.