Looks like the amount of games considered to be the best in a given year started to contract after the huge explosion in 2008. What happened after 2011?
That said, this list is all over the place and might reflect the biases and demographics of wikipedia editors.
Off the top of my head, I loved Tony Hawk Pro Skater 2 and Jet Set Radio, but putting them next to Deus Ex, Thief, and The Sims in the same year, each of which respectively defined groundbreaking new genres, hints at a strange or inconsistent criteria.
Another incoherent juxtaposition is putting Burnout Paradise and Gears 2 in the same year as Braid, which was a pioneer in the indie renaissance, and Grand Theft Auto 4, which was a massive technical leap forwards, particularly in reactively blending animations and physics.
It seems as if the editors of the list can't come to an agreement over what the list represents: the most groundbreaking and influential games of their time, or just games that were generally considered a good time at release.