Fallout 2, I didn't expect to like a RPG with those settings so much.
Same for Myth (edit: but not for the settings, I just didn't expect to like a RTS, although Myth games can more correctly be defined as "real-time tactics", not "real-time strategy")
Gothic, never heard of it when I got it cover mounted on a gaming magazine.
Thief series and the first Deus Ex: I expected to like them, but they even exceeded my expectations (even Thief III, despite its flaws).







