SSI's "Gold Box" Series, particularly The Pool Series, the Savage Frontier Series, the Krynn Series, and Dark Sun Series.
Of course I Also Love the Innovative ones like Wallenstein 3-D and it's decedent DOOM, and of Course this board would not exist if it weren't for the Infinity Engine and the Baulder Gate series that basically resurrected RRG and it's decedent the Aurora RPG Gaming Engine and RPG Campaign Development Tools (mouthful, though calling the package "Neverwinter Nights" after it's Demo module might have been a bad Idea considering most consider it "just another CRPG game") that that did what the Gold Box's "Unlimited Adventures" could not....create a new way to run D&D Campaigns and be "the "Kazza of network RPG gaming" for those that wanted to develop their online persistent worlds that shared computers instead of being on a central server.
And of course though they were often buggy, the Ultima Series...specifically Ultima 7 and 8.