MGS4 is an absolute MUST BUY......it to me defined the reason for spending £425 on the PS3.
R & C I would say is a very fun game with a huge repeat value.
GTA 4 -- only get it if you didn't like the open-ness of GTA SA...n loved GTA 3 & GTA : VC more than GTA SA
Uncharted -- I have heard this is a very nice game
That leaves two...I say WAIT for 2 months as Little Big Planet & Motorstorm 2 might interest you
All hail the KING, Andrespetmonkey