I tend to go through gaming 'seasons' once in awhile. My current season being Action/RPG with Horror/Survival coming soon as a transition. Left4Dead and similar (like Serious Sam) qualifies for the prior more than the latter in this case.
As of now, I've been playing games like Legend of Zelda (just beat Link's Awakening), Magicka (beat the first part), and catching up on some Fallout3 (Working on the SurDIEval Guide) and Borderlands as Lilith this time (Playthrough 1, and Mordecai is Playthrough 2 (not started); playing her for the challenge, and to co-op with anyone (namely my brother which is Mordecai this time around), and though she takes a bit of time to learn, Lilith freaking rocks. Worthy of the Difficult But Awesome trope).
I think next on my agenda will be probably restarting F.E.A.R. (first one), taking on Amnesia (maybe broadcasting it), and seeing if I can finish Parasite Eve 1 (which I can still find time to play). At the end of the horror/survival season, I might go on a cerebral break, and transition with some puzzle games (dedicated time to Spacechem, Toki Tori or Recettear) and maybe run into a nostalgia season along the way.
Actually, I think nostalgia seasons hit more frequently than regular seasons, and are essentially random what games I play for the week. I mean, I can make a surprising amount of progress in Spyro the Dragon or Crash Bandicoot, or just outright beat some games in a single sitting/day, like the classic Mario/Sonic games.