Hmm hard question.
Back in 1993 it was Doom, which looked very beautiful at that time. In 1996 it was Quake and Duke3D. Later Ascension and Morrowind. So it always changes <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" />
Soon it will probably be Farcry, Stalker, Doom³ and HL². But eye candy isn't all <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />