For me its 2006.
2012 was a good year, it's just that a lot of the bigger ips in gaming ended up having disappointing games.
2006 only had 6 notable games that I can think of.
Gears of War
Elder Scrolls IV: Oblivion
Legend of Zelda: Twilight Princess
New Super Mario Bros
Wii Sports
Final Fantasy XII
The only game I was a big fan of was Elder Scrolls IV: Oblivion. Twilight Princess was good too but to me was disappointing.