http://en.wikipedia.org/wiki/Merchant_Prince_II
holistic design's merchant prince was excellent. insanely replayable.
but holistic's best work (in scope, maybe not so much in execution) was:
http://en.wikipedia.org/wiki/Emperor_of_the_Fading_Suns
http://www.kborek.cz/forum/phpBB2/
emperor of the fading suns: which is still one of my favorite games to play. the problems with the AI were (to a great extent) modded out by fans over the years. if you can ever find a copy, and you like turn based war / politics / strategy / science games, check it out.
http://en.wikipedia.org/wiki/Ascendancy_(computer_game)
ascendancy was better than master of orion once they actually put an AI into the game.
by the time they did, it was already in bargain bins and had been basically trashed by reviewers the world over.
http://en.wikipedia.org/wiki/Boiling_Point:_Road_to_Hell
xenus / boiling point: road to hell, was another post-patch keeper. when it was released it barely ran. but under the bugs was an open-world FPS with very interesting (and pretty complex) role-playing elements. imagine stalker but in a chauvinist, 80's action-movie version of a south american banana republic.
you roam around doing missions for the military, the junta, the indians, the narco-thugs, etc, all while unraveling one of the most hilariously over-the top plots i've ever come across this side of a duke nukem game. the graphics were amazing for what they attempted to do (open map, no loading screens, free movement from the start). after the patches (it REALLY needed them) it played really well. i think atari still has the rights to it in north america.