Lol, the lists I could give...
I always cycle between Kinetica and Devil May Cry on my PS2 and Chrono Cross on my PSX. They never get old.
Halo is great for 15 minute breaks from anything, really.
Skyrim for the PC is a deathtrap as the mods keep the game interesting way longer than it could on its own. I went vegetative when I loaded it with immersion mods. :P
Tekken, Marvel vs. Capcom, King of Fighters, Alien Hominid, Battleblock Theater, Castle Crashers, Castlevania, etc.
Silent Hill and Resident Evil have always had a special place in my heart as well.
If you're into handhelds, 9 Hours, 9 Person, 9 Doors is easily one of the best games ever made. Haven't finished the sequel yet though.
On the note of greats, The Longest Journey games are also in my top 10. I have them for PC.
If you're into immersive MMO's you might like The Secret World. The ARG's for that game are unbelievably good and the community is awesome (last I checked anyway.) I stopped playing because I wanted my creative pursuits to feed my writing and creative works rather than a character I could've easily lost myself in. The ARG's and role-play are so good, I didn't want to fall victim to them (if that makes sense.) It doesn't help that stuff like that fascinates me though, so you may not have that problem.