I completely disagree - 2D games aren't dead at all. They're just not as common anymore. All those free flash games that keep appearing on the Internet - Aren't they 2D games too?
One example of a commercial 2D game is Peggle by PopCap. :P That was released on Steam a few months ago, and it turned out to be quite popular.
Even Yahtzee reviewed it on Zero Punctuation, and click this link and listen to what he has to say 'cause it also rings true to the current situation regarding 2D games.