I've usually got 2-3 games I'm "playing" at a time. And though thinking about it now made me just realize this, I typically stick to one console, one handheld, and one PC game. Like, right now I'm playing StarCraft, Fire Emblem: Sacred Stones, and Jak II.
Once I beat StarCraft I'll move on to StarCraft II, then I'm gonna get back into Diablo for a little bit
Sacred Stones is gonna lead me into Fire Emblem: Awakening, then I'm gonna run through Kingdom Hearts 3D after I finish with those.
Once I finish the Jak & Daxter Collection on PS2 I'm gonna play through Darksiders again before starting Darksiders II.
That way I've got games to play while I'm at home, while I'm on campus, or none of the above