I'd say:
1) Star Control II
2) The Fallouts (1,2,3,NV,4)
3) Tie between Skyrim/Oblivion/Morrowind and
3) Mount and Blade: Warband (single player only)
4) Any Infinity Engine RPG (Baldur's Gates, Icewind Dale, Planescape: Torment)
5) Multiple Open World Games (only the good ones) like Dying Light, Shadow of Mordor, etc. (not Assassin's Creed or the Arkham games)
6) Space Pirates and Zombies!
7) Civilization 2, 3, 4 and 5 and Alpha Centauri (too bad Beyond Earth was garbage)
8) Oh my God, I'm missing so many and I've already listed like 20... ummm...
9) The old HOMM games
10) Deus Ex 1 - everything after that has been a drag
11) Still waiting for a good Warhammer 40k game, which will go here *crosses fingers*
12) Wait, how many were we supposed to list?!