I've got an Alienware MX18. People are going to shout me down, but the SOB is almost four years old and still going strong.
A rig like mine nowadays starts at approx 1300 quid.
I run RTS games on it - unlike shooters they need a whole lot of power (mine runs vCoH flawlessly)
Having said that I get my desktops from Cyberpower (excellent UK company, great customer service). For the same price they do some badass gaming laptops...
Fangbook Evo
CyberPowerPC FANGBOOK EVO 17.3" FHD LED-Backlit 1920x1080 Display w/ Red backlit performance keyboard with programmable keys, Built-in 720p HD webcam, HDMI Port, Li-Ion Battery, & Universal AC Adapter...Intel® Core™ i7-4700MQ Mobile Processor 2.40 GHz 6M Smart Cache, Max Turbo Freq. 3.40 GHz
The Alienware has: 4th Generation Intel® Core™ i7-4910MQ Processor (Quad Core, 8MB Cache, Overclocked up to 4.1GHz).
I'm sure some of our more tech-minded members will be able to split the difference for you. The main issue with laptops is design - optimal performance plus cooling and extra slots. This ain't an issue with a tower, but it is with a lappie. This is why you get what you pay for - my Alienware rig is very quiet and performs well but runs dry very quickly - it needs to be plugged in for gaming.