|A short list of well-done games would include heroes, lbreakout2, bzflag, freecraft, frozen-bubble, powermanga, chroimium, crack-attack [*], liquidwar, xevil, nethack, billard-gl, (race or trophy — I don’t remember which on eis good), enigma (very frustrating, though), castle-combat [*], pipenightdreams.
This is a pretty wide range of games. Some have very nice graphics, others don’t but were included because they’re fun to play. Not all of them are equally fun to play for me, especially some of the more “puzzle” oriented games (eg, pipenightdreams?), but..
Games marked with [*] are multiplayer-only. I didn’t include freeciv since you excluded civilization clones.