User communites in the past have provided reason enough to buy games, but the last ones I can really think of were in the late 1990s where content was easy enough to make that a couple of college students could produce a worthwhile map; and everyone could create a custom character model if they wanted. User created content for consoles is a different beast that it was for the PC a decade ago, and few games have had decent tools to create content or a nice way to ensure that users mostly deal with the best user generated content.
Now, I think most consumers see user generated and downloadable content in the same light ... this add on content is a nice feature, but the game has to justify a purchase with the content that is on the disc.







