Miles Quaritch
Member
The two I mostly use (especially for pre orders) are TGC and Simply Games
http://www.thegamecollection.net/
http://www.simplygames.com/
Both probably the best sites I've used and stupidly quick delivery. If you pre-order, you'll likely be playing early.
TGC used to get games to me a day or two before release, haven't used them in ages though so I don't know if that's still something they offer/are allowed to do.
Simplygames is pretty great too.