Wow, I don't agree with quite a few of these! But I guess that's why it differs from person to person.
Portal 2 is one of the games I regret buying at full price. Fantastic game, but 12 hours for the single player + co-op left me feeling disappointed. The level editor has made me feel slightly better about my purchase, although the fact it's been constantly marked down to peanuts in the Steam sales hasn't. I could have bought it for about £8 by the time the custom content had come out.
Uncharted 1 was very short as well. Luckily, I didn't pay full price for it :P
As for games that are actually worth full price, not many in my own opinion. Orange Box was worth it. LittleBigPlanet 2 was worth it (for me) but I had a lot of interest in the level creator & custom content. Xenoblade may well be worth full price too, haven't played it yet. The best thing about that game is that I bought it for £10 three weeks after it came out because Gamestation seemed to be flogging all their copies for some reason. Couldn't believe my luck.
