As others have stated, Planescape: Torment, Balder's Gate 1&2, Fallout 1&2. I would also add Arcanum to that list of RPGs. For RTS, I would try Company of Heroes or Dawn of War, both of which are pretty good, though DoW could have used a bit better balance in the later x-packs. For hard as nails strategy, I would highly recommend Commandos and Beyond the Call of Duty. If you want turn-based, I highly, highly recommend Jagged Alliance 2 as well as Unfinished Business, both of which I still play at least once a year. Two great 4X games would be Galactic Civilizations 2 or Alpha Centauri/Alien Crossfire (SMAC and SMAX). For simulator, Roller Coaster Tycoon 2 + xpacks would be at the top of the list, and Locomotion is pretty good as well. Most of these can be found on gog.com