Do you think the graphics card in the iMac is good enough to play current top-notch games? is the processor? Is the graphics card better than the one in the MBP?
It won't play top games at high settings at native resolutions. I would guess it will play them probably on medium settings at < native res quite smoothly however.
We're going to need to wait until someone finds out if the iMac is using the desktop or mobile versions of these cards.
Still, the MacBook Pro is using the top of the line midrange for laptops. I've only seen the 8700M GT in 17" desktop replacements and the 8800M GT still isn't out yet.