When have people started to basically judge a game based on length alone?

[TK14]

What's that? Oh, sorry, I was too busy playing Xenoblade Chronicles' 150 hours of content while appreciating its high quality, captivating story, expansive world, gorgeous environments, deep and engaging battle system, memorable characters, and incredible music....

:p (just teasing a little, don't hate!)

In all seriousness, I think the length of a game comes into play so often because when people like something, they naturally want more of it. So for a game that's fantastic, but only 5-10 hours long, that length can be seen as a negative. Of course, it works the same in reverse for overly long games if people don't like them. Though in that case, they are less likely to blame the length itself, and instead blame the low quality or lack of fun to be had. Also, for those short, but fantastic games, the length is the only thing most fanboys and trolls can objectively "pick on." Whereas, again, for the longer games, if they aren't worth playing to the end, it's more likely that something else about the game will be blamed.