Halo, Gears and COD. Probably the most popular franchises at the moment. People will also want to stay on the hamster wheel of achievement collection.
Why is that? Because the 360 completely outsold PS3 and Wii?
In the end, I don't think it matters which machine will be the most powerful.
The 720 or whatever is going to completely outsell the competition.
And I think it does matter which will be the most powerful. Because in console war history, it was always the least powerful that came out on top. So making the most powerful console might really not be such a good idea. If history repeats itself, it will be Wii U > X361 > PS4 then.