Alienware is way overpriced...
The best gaming laptops are by Gateway. I got my P-7805u for $1400 last summer.
It sports a 1GB 9800GTS, C2D @2.6ghz, 1920x1200 screen and it can run Crysis...ful res, mix of high/very high settings. All other games run great maxed out. The newer version comes with a GTX 260, and only 16x14 screen.
Asus also has pretty good gaming laptops, but nothing can beat a decent Desktop...