Half-Life 2, Episode 1 and Episode 2 with the 30GB Fakefactory Cinematic Overhaul Mod.
Absolutely fantastic in every aspect. Well worth the massive download.
Mass Effect 1 and 2. Got ME3 as a gift but decided to run through ME1 and 2 to get back into the story before I play ME3. I must honestly say that ME1's story / campaign felt a lot better than ME2. ME2 just has you run around recruiting a team with some story bits inbetween. Still a good game, but could have been better.