My suggestions:
(which will probably be pretty much the same as everybody elses)
The Orange Box (Several games all centred around Half Life 2, something of a bargain)
Call Of Duty 4
Call Of Duty 2
Bioshock
Crysis
They're all first person shooters (fps's)
You can now get Timeshift for £13.00 from Play.com, a game which a couple of members here have recommended. At that price, I've just ordered it, it's still £35.00 in my local GAME Shop.
I'm also fond of Oblivion: ElderScrolls 4, a role playing game, which can be picked up now for £20.00 including both expansion packs in High Street GAME shops or online. Play.com prices include p & p btw.
I also like:
Painkiller Black Edition
Painkiller Overdose
FEAR & The 2 add-ons
Roller Coaster Tycoon 3 & The 2 add-ons
Civilisation 4 plus add-ons
MS Flight Simulator X (recent expansion pack has also been released)
TOCA Race Driver 3
Most of the Need For Speed series
Dreamfall 1 & 2
Syberia
Dungeon Siege II Deluxe Edition
Far Cry
Max Payne 2
That'll do for now
Check out play.com; GAME and HMV online and in the high street, lots of good prices right now.
To play flight simulators a joystick is recommended.
To play driving/racing games at least a gamepad is recommended, preferably cordless. I'd recommend Logitech Gaming hardware
If you're rich get the Logitech steering wheel, it's only £160.00