#30: Guitar Hero 2 (2006)
XBox 360, PlayStation 2
There's no doubt the Guitar Hero franchise is one of the defining icons of this gaming decade, but singling out a particular entry is tough. The original is certainly a candidate, as is World Tour, which appropriated the Rock Band idea of four-player fun. But the one I personally had the most fun with was Guitar Hero 2, which had the perfect mix of on-disc songs, co-op action, appropriate difficulty, and replayability. Let that stand in for the entire franchise here, as the gaming name that brought plastic instruments into every gaming household.
#29: Halo: Combat Evolved (2001)
Once again I'm letting one title stand in for an entire franchise here. Halo is not, and has never been, the best first person shooter, or the most innovative, or the one with the best story. But by some indiscernible magic it's the one that penetrated a sports-loving car-tuning pot-smoking beer-guzzling male demographic and made them hardcore, committed XBox gamers. It's the franchise that sold a million systems and its protagonist, Master Chief, has become the Sonic or Mario of this gaming decade. And you know, it's not a great game, but it's a pretty damn decent one.
#28: Phoenix Wright: Ace Attorney (2005)
Each and every one of the Ace Attorney games is equally wonderful so I may as well highlight the original. These courtroom detective stories ride entirely on the quality of their convoluted, hilarious, heart-pounding scripts, and it's amazing that through iteration after iteration that quality remains undiluted. Playing an Ace Attorney game combines the best aspects of a point-and-click adventure and a well-written pulp detective novel and it's hard to see how anyone who's interacted with one could fail to wholeheartedly love it.
27: Disgaea (2003)
This is the best turn-based strategy game ever made. No ifs, no buts, this is it. It doesn't leave room for improvement. Levels of depth are themselves built on levels of depth; whenever you think you've fallen all the way into the game another trapdoor opens beneath you offering hundreds of hours more play. Characters level up, who hold items that level up, which hold within them multi-level dungeons which themselves contain items and characters. A political system allows you to pass votes to rewrite the laws of reality; at the point when you've done everything you can vote the game up to yet another iteration of difficulty and the hunt begins anew.
26: Devil May Cry (2001)
God of War isn't going to feature on this list, for three reasons: it came after Devil May Cry, it's derivative of Devil May Cry, and it's less enjoyable than Devil May Cry. Everything that Kratos did, Dante did first and better (although I'll give Kratos credit for all those threesomes, Dante hasn't yet gone there but it seems fair to give him time). The smooth, free-flowing aerial combat of DMC gave birth to the "stylish action" genre which includes such entries as God of War, Wet, and Bayonetta, but despite it all DMC remains the bar that the others have yet to jump.