2017 and 2007.
Mario Galaxy, Bioshock, the OG Modern Warfare, Portal, Team Fortress 2, Halo 3, Metroid Prime 3, Crysis 1, Mass Effect 1, Assassin's Creed 1, Rock Band, etc. 2007 was easily the most exciting year for gaming of the 21st century, with so much innovation and great new series.
2017 is the best year in overall quality.