Silent Hill. This has been increasingly hard for reasons that I'm sure you've all heard 8 bajillion times and have also probably heard from Yahtzee as well but I still have a fondness for the series regardless and whenever some mentions the movie or 0rigins or Homecoming I'll either go back to the previous entries or I'll use the silver linings of those games as defense and mumble the rest away. Maybe it's because there hasn't been a single other good horror franchise in video games ever. I don't really regard Resident Evil as horror and really its always come off as a comedy to me, and while I do like Resident Evil I still stand by my statement that Silent Hill is the only video game horror franchise to have ever worked as horror at all.
Oh, and Doom. To be fair Doom doesn't need to be defended seeing as its extremely important to the industry as a whole and even haters can't deny the impact it had (For better or for worse, seeing as how shitty most shooters are) but I love this game so much that my inner nerd starves to death without participating in the online Doom community which is surprisingly large and thriving and he will also starve to death if I don't feed him new .wad files to sample.
Then there's Fallout. I love classic Computer RPGs, its a shame they had to go and die when the scourge of J-RPGs showed its face. So Fallout 1 & 2 rank high up on my favourite games list because they're one of the few classic style RPGs post Final Fantasy to stand up on their own, and while I sort of want to be a No Mutant's Allowed biased dickhead to Fallout 3 and say Bethesda butchered the series, I would be a big fat hypocrite because I really liked FO3 and you bet I'm drooling over New Vegas right now, especially since some of the original devs are on board giving me hope that it might actually bring back the dark humour and make the RPG system a bit deeper than the watered down Bethesda version.