While I voted "usually rushed", it's more complex than that. The insane deadlines on video game tie-ins is a killer (production windows of six months is not uncommon, which is insane).
However, that's likely not all. First off, how many people get into the industry to make tie-ins? I imagine the people working on the product are demotivated and understandably may have trouble giving the prerequisite number of fucks.
Secondly, you're usually tied on your hands and feet with little to no artistic license. The game needs to follow the game closely, which means the studio isn't free to adapt the game properly to a different medium.
Thirdly, I hear the movie producers tend to be kind of dicks about sharing what the game studio need to do their job. Scripts and such usually end up arriving fairly late, so the production is difficult to plan out.
That's not to say that there's something intrinsically wrong with games based on movies. It's the tie-in model that's problematic.
As to the thread title question, I'd love to see a Carnivale game. The setting and aesthetics are plain amazing, and I think it'd make for a fantastic story. It probably wouldn't sell too well, though.