In my humble opinion, game developers typically don't do a very good job at "changing" games. If you change something it takes away from the previous so called "awesomeness" of a game and then they lose sales. Am I wrong to say that? Now I'm not dissing Bungie, Halo is pretty fun. But all of the Halo games are the same. You run around a map, shooting aliens. A lot of games are like that. Run around. Shooting Something.
And the guys that are designing and building the levels are the same type of people that design and build the CGI for movie work, it's usually just a much higher resolution.
If people want changes in their movies, then they need to go see other movies than just the high budget blow em up movies that come to the theaters. Look other places for movies like film festivals and lesser known directors. If people want changes in their games, they need to expand their genre of games past first person shooter games. There are so many different varieties out there, you just have to look for them.
No, I think you misunderstood my statement was more in line with people still playing Quake 3, or UT2004, not that developers don't like to try and keep a series fresh.
People still play old old games, hell some people still play CS1.6.
This just means that people don't like to change games, when you get good at a game, the next game in a series is USUALLY WORLDS APART, because hey, you were good at the one before, and it got built into you... the slighest change throws you off.