Ive got just cause, erm its not really a driving game u can drive yeah and do great stunts, but the handling is awful lol. So unrealistic, its fun to explore the island etc, but if ur after a fun driving game then i wouldnt recommend it.
Also got GTR2 and yeah its very realistic, if u want to have fun then i dont recommend this unless ur prepared to spend ages tweaking the car, and getting used to the controls. Personally its too much for me, too realisic, i prefer fun arcade races like midtown madness, not realistic but good ol fun.
Oh also ur gfx card might not be good enough for games like Just cause, or u might have to play lowish res.