No particular order:
Baldur's Gate series - overall, just one word - AWESOME
Planescape : Torment - one of the few games, which do actually have a great storyline.
Dead Space 1&2 - for combining so many genres correctly. 3rd part was lame, though the storyline was well done.
Half Life series - I don't care that Gordon Freeman didn't say a word. He is still one of the best characters
TES: Oblivion - Skyrim and Morrowind look odd compared to it.
Fallout series - first two parts for wonderful tactical game, Tactics for improving that tactical knowledge, 3 for well written stories
Diablo 2 - just please don't mention 3... 2 was too awesome.
Deus Ex series(though HR left me conflicted)
Max Payne - BULLET DIVE!!!
Serious Sam - who doesn't love Sam "Serious" Stone
Honorary mention - Assassin's Creed 3 - great game, but worst ending in whole gaming history. PERIOD. Open up new thread and PM me if you want to discuss that.