Generally when the quality starts going down, but also too much of something good can be bad.
COD is an example of a game that's declined in quality as the series has moved on (it's still not bad though)
FIFA is an example of a game that's gotten better over time but I don't buy them every year, because it's too much. By the the time FIFA 13 rolls around I'll just be done with FIFA 12, and won't feel like playing a football game for a while.








