Portal was amazing. Granted. Portal 2 was amazing too (although it delved too deeply into the dark underbelly of retcons). Still, I think everyone remembers it as gleaming gamer gold that can stand the test of time, and it really hasn't. It was a fun romp the first time, but it has no replay value, which is something I consider very important, and it was bloody short. No, short would be fine, Heavy Rain was too, but Portal was practically a gaming milisecond.
No matter how fantastic the experience, if it doesn't last x amount of hours, I don't even remember it. I know a lot of people are the same. What is it about Portal that justifies that? Funny jokes? I can listen to Louis C.K. or Gabriel Iglesias or George Carlin if I want funny jokes.
Valve didn't consider it that important when they released it either, just a grab bag of puzzles with a technology they were testing that they upgraded into a mini-game. Ohh! That's IT! That's what Portal was. A MINI-GAME. I just figured that out! No, Fable 2 is a game... but it wouldn't be fair if the Chickn' Kickin' mini-game got nominated for game of the year, so why is it OK for Portal? Because it's better? Because it's Valve?