Elder Scrolls Oblivion

The music, scenary, quests, and guilds are perfect. Everything about the game is perfect, even the shitty NPCs and bugs that were never patched. Glitching through the Arena wall so that the opponent could never kill you, duplicating scrolls soon after you left the sewers, joining the Dark Brotherhood, using 100% Chameleon on Thieves Guild quests, the list goes on. The music is beautiful and the potato NPCs was what made this game special. I hope for the next Elder Scrolls to be something similiar but I doubt it, Bethesda's on thin ice.

Crackdown

The first and second Crackdown games for the Xbox 360. I think it's worthy to be on my list simply due to the amount of fun I had on that game whilst playing with my friends. The third and latest one was a bit shit.

Team Fortress 2

Self explanatory really, what's better than sniping heads off whilst being called a hacker by RED who kills you with bodyshots? Oh, and crits are balanced ;)