Masters Of Orion, the original Warcraft Orcs and Humans, Duke Nukem 3D, Star Control, Wing Commander, Black Thorne.
Most of these games blow current games away in playabality and pure fun.
There was really nothing to do graphics wise back then, so everyone focuses on pure fun factor. Now you get too much time spent on graphics and not enough spent on fun.
Now don't get me wrong, all other things equal I would rather have a Quake3 graphics than Duke Nukem, but Duke was sooooo mcuh more fun.