Actually, I might be able to make a top 5. I needed to write out every game I've ever played to figure them out though (which it turns out, is 41 total, more than I thought)

PC forever: Sims 3, Tomb Raider Legend, Skyrim
Xbox 360: Mirrors Edge
Nintendo DS: Elite Beat Agents

Tomb Raider Legend is my favourite because it's nice and short and fun - and the only TR game I've ever completed. And at the end you get fucking Excalibur, which is a fucking one-hit-kill AOE weapon which basically makes any playthroughs after a OP bloodbath if you equip it. Perfection. [s]Sims 3 is a returning favourite because of my secret god complex.[/s] Mirrors Edge is again nice and short and fun abeit really fustrating in places (and again one of the very few games I've finished), and you get this amazing sense of freedom playing it. EBA is just... fucking EBA. Even though my friend nearly broke my DS playing it.

Rayman 3: Hoodlum havoc gets a honourable mention for being [url=http://laurendem.files.wordpress.com/2013/08/r3hd_x360_screenshots_25.jpg]stunning[/url], even though I never got very far.

Skyrim is just... brilliant. As for favourite quests though? Idk. Probably Forbidden Legend. I can tell you my favourite cave though - Yngol Barrow. Also have an [url=http://imageshack.com/a/img341/7294/ohnoskyrim.png]old screenshot[/url]. ...I might go back to it at some point actually...

Games I didn't like? Sonic Heroes, Sonic Mega Collection, the Phoenix Wright series (or at least 1-3, the ones I played) or Assassins Creed 2 lololololol.