I think our finite amount of time and money to enjoy games also contributes to why overexposure is a bad thing. I think we all can agree that too many Guitar Hero games have been released. Do you know what really makes me disinterested in them? It's simply the fact that because they come out so frequently I don't have the time to fully enjoy them. One game comes out while I'm still getting mileage out of the other one. It becomes apparent I'll have to skip one or, if I want to play all of them, put off getting the next one until I'm done with the one I'm on. But if the rate is too frequent then I never catch up and the whole thing becomes intimidating and a big chore.
This reminds me of when Thoreau went to some library in Concord or thereabouts, and after seeing all the books he wept because he realized he couldn't possibly read all of those books in his lifetime, no matter how much he read.
Video games are now at or near that point too, and they come out a lot faster than it is humanly possible to play them all. Back in the 16-bit generation and earlier, someone could probably keep up on all the games (or at least ones worth playing) provided they had enough money to afford them, but now that's impossible.
There are so many games I've missed out on and continue to miss out, and I will never have the time to go back and pick those games up because new ones are piling up too fast to keep up with. There are so many great games that come out and DESERVE to do well, but they don't do well because they are drowned out by the 10 millionth reiteration of call of doody, Madden, and so forth. These are real time eaters. They're fun and definitely worth it if you like that sort of play (if they weren't people wouldn't keep buying them), but it forces you to miss out on the new I.P.s. Some players get sick and burned out on these games, but there are too many others who keep buying them for them to ever really fade away like they should.
I think this is why new quality IPs like No More Heroes flop... everyone is buying 20 different versions of Mario for their Wii, so they have little time or money to try out new stuff.