I'd recommend Icewind Dale, it was one of my favorite RPGs back in the days.
Nvm, the requirements for Icewind Dale was slightly higher than I expected. But, I have another good RPG to reccommend - Might & Magic VII: For Blood and Honor. I've played it for numerous hours, and it's just a really fun game. Hell I even replayed it less than a year ago as it's just that awesome.
Other games worth mentioning:
Age of Empires
Age of Empires II
Diablo
Heroes of Might and Magic II
Heroes of Might and Magic III
Jazz Jackrabbit
Jazz Jackrabbit 2
Starcraft
Worms 2
Worms Armageddon