Honestly i agree with the post talking about 2d graphic classic.
Those were the truely most original games, and they were fun. Super Mario, Sonic, Donkey Kong...etc. Those are the games you can spend hours on. It could be that, diablo, HL1, doom are classics, but i would consider them as modern classic. Not ORIGINAL CLASSIC.
Its, all about the graphic quality now, just about making it better and more realistic.