It seems like I'm eternally playing abadonware and forgotten classics.
I highly recommend The Underdogs. I've contributed to that site over the years (games, links to underdogs, etc) and the people who run it are a great bunch of guys/gals.
There are hundreds of unknown and underrated PC games like Albion (I own it).
One really can't be a console only gamer, never could, never will. There are far too many great games on the PC that people don't even know about ("There's nothing but FPSes and RTSes on PCs").
Seven Cities of Gold - I still play this every now and then.
Ultima IV-VI.
Syndicate.
Cliff Johnson's puzzle games - The Fools Errand and 3 in Three. You can still download these from his website (www.fools-errand.com)
Anything by Infocom, esp. Trinity, A Mind Forever Voyaging, The Lurking Horror, and the Enchanter Trilogy. Play some of them here: http://www.xs4all.nl/~pot/infocom/
I've always wanted to try Sundog: Frozen Legacy, but I could never get my ST emulator to work...