Nearly every review I've read of Portal 2 has said that it, unlike the first game, is too long. The first Portal was a perfect length, and Portal 2 can't hope to match that same level of brilliance by being as long as it is.
The thing is, this isn't really dissuading people from giving the game sterling marks. Now, I'm certain that Portal 2 is going to be amazing – Portal is one of my favourite games of all time – but essentially, this brings up that same argument of "length = value". Indeed, the only site I've seen criticize Portal 2 for being too long and actually sticking by that has been Joystiq.
So a game can be heavily criticized for being too short, but being too long isn't a problem? If this is the case, then once again, we see reviewers treating games as products rather than experiences. So many great games from years past could be "beaten" in an afternoon, yet they had so much replay value that even when you were spending $50 – $80 in some cases, you really got your money's worth. Just because Portal was only a two-hour long game doesn't mean that its brilliant, tight gameplay and amazing writing weren't worth full price – it just means that people have a skewed perspective on value.
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There's always a value problem with most writers in relation to games, for whatever reason. Either "hur hur game is too long" or "hur hur game is too short," rarely with reasoning outside of "hur hur I paid too much." Endemic specifically to games, mostly because gamers have no ability to discuss games maturely. Why do we still spend tons of time discussing how great the game's textures are? It's a silly discussion outside of technical documents by nVidia, but it's recapitulated by game writers all the time. To say a game is beautiful is fair, and to discuss why is fair, but not from a technical perspective. I didn't find Wind Waker beautiful because it could tesellate the water at some rate or render graphics in some manner. I found it beautiful because of aesthetic choices made by the creators (such as the use of pastels and horizons). Let's talk about Wind Waker Matt!