Perihelion is an awesome game, obviously under-rated, with brilliant fantasy-scifi background, great music and sound, nice graphics and good SSI-like battle system. I had a great time playing this game in 1994.
Ishar serie is a good classic (i prefer the 3rd installement). Play Crystal of Arborea first to start with Ishar 0.
Then, if you like Dungeon Master like games, there is of course Black Crypt and Captive.
