I want StarCraft 2!!...
Now seriously, a game that deserves a DECENT sequel is Blood. Blood 2 was not good and didn't had the charm of the original one so, in my opinion, a Blood 3 would be nice.
AN ACTUALLY GOOD BLOOD 3.
Also a Diablo III. Seriously, Blizzard could milk as much money from Diablo as from Warcraft, but godamned Blizzard North had made it so craptastic that Blizzard shut them down.
So I think they deserve another chance. Diablo is still has some adepts and is still winning adepts, specially Diablo 2: Lord of Destruction.