<being pointless rant that should be ignored>
Tom, I kind of disapointed with you. How on earth did you not include, among the game nominees, at least one of the following, all of which have a similar theme, although vastly different sorts of gameplay, and were probably a direct product of Portal:
Also, for its sheer originality, why not:
Don't get me wrong, all the games you selected are very good (except The Torture Game 2 and Gemcraft, to be honest) and I'm particulary happy that you opted to include some very unorthodox games such as The Majesty of Colors and :the game:, but surely one the previous games deserved a mention?
<end rant>