First of all, I want to make it clear that this should be a healthy argument without flaming. This is purely opinion on the most overrated game. If you give an overrated game, give a reason why you think it's overrated. If you disagree with someone, give reasons why. But do not get out of control with the arguments. Just want to make that clear.
Personally, I'm thinking Super Mario Galaxy at the moment.
It was an okay game. It was relatively easy (can be beaten in a matter of days with a healthy amount of hours put into it). It felt kind of repetitive, in my opinion. The 3D, Galaxy-type platforming is something I find rather annoying and not quite as revolutionary as it's made out to be.
But most of all, it gets praised like there's no tomorrow. I've even heard talk of people calling it the best game ever, which is ridiculous. Even if you like the game, you have to admit that there are a lot of retro games that deserve that title much more.