I have to agree with Omega, but I think we're comparing apples and naartjies here.
No serious gamer will be content with an iOS game, but taking my own iPhone gaming habits as an example (I play perhaps two or three times a week when I'm waiting in a queue, having morning coffee, etc.) it makes no sense to me to pay so much extra for a dedicated gaming console.
To me this is like when people say Android devices far outsell iPhones without acknowledging the fact that the sheer number of Android handsets far outweighs Apple's single handset; similarly, because of the sheer quantity of iOS games and their low price, naturally they're going to be popular because it's a cheap addition to a device you already own.
Now if someone could just whip up a decent Mario clone on iOS we could settle this permanently