I have a lot of favourite games for the PC, but I mainly played them in earlier years. The entire Myst series, especially Riven and Revelations; Grim Fandango; Monkey Island 2; American McGee's Alice; Final Fantasy XI; Day of the Tentacle; Kings Quest series; Starcraft 1 and 2; Warcraft 3.

I'm sure there's heaps more, but I can't think of them right at this moment.