User generated content is fine as long as it's something that's used to lengthen the replayability to a game. I am not a fan of it at all when it makes up the majority of the game. Someone mentioned Blast Works earlier and I think that this is a perfect example of what I dislike about how user generated content is being used. There is not much of an actual game at all and the level editor is basically the meat and potatoes of the entire package. It's a shame because the campaign is fantastic and if more of it existed, Blast Works would be a top rate shooter. It is worth the price that you can find it now though.
Also, I find user generated content to be a bit of a cop out by companies and it could be troublesome to gaming in the future. It's kind of like reality television in the way that it can be used to cut jobs. The way that reality television cuts jobs by not needing to pay writers or directors, games with user generated content can get away with having less programmers, artists, etc. Furthermore, this can make for a lot more "amateur" games. In other words, leave it to the pros.
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"There are like ten games a year that sell over a million units." High Voltage CEO - Eric Nofsinger
