There is a very interesting article on Anandtech about this.
The two part article asks what's the best GPU and CPU for Oblivion. It uses Oblivion because the game has the highest graphics requirements of any current game.
Basically, the article says that dual card GPU setups are, basically, the only way to play the game with decent frame rates and, if using a dual GPU sretup, a dual core CPU offers significant performance advantages.
Bottom line? ATI X1900 crossfire coupled with an an OC'd AMD FX-60 offers the best performance--almost acceptable frames rates with most details turned up. THat set-up offers framerates nearly twice of single GPU/single CPU set-ups.
I suppose one could extrapolate that into laptops. That is, a decent CPU coupled with the nVidia Go 7800 will play most games currently out very well. But if you want a rig for the future, one that will play games like Oblivion and future titles, you'll want SLI or Crossfire + dual-core CPU set-up.