I would say Amazon just for the DS clearance in May or June when they had the Electric Blue old-style DS Nintendogs and Animal Crossing bundles for $100, plus a free toy from Toys R Us to boot. Of course, that was back when they were partnered with TRU.
Although I did order from EB a bit in the first quarter of the year before they really got taken over by GS, I'll go with YesAsia for my one flawless order.
Overstock.com would have gotten my vote, but their shitty cardboard envelopes just don't cut it.
buy.com $20 off $50 for like 5 months how could you say no. New 360 games for $40-$45. They became cheaper then play-asia on games. Plus they have, movies, and books.
Play Asia, for hooking a brotha up with wii compony cables cheap, 360 vga cables w/ optical cheap... and there is no ass rapin with the shipping too. Plus, if an item is out of stock, they will notify you when it is available, i can dig that.
Because of the region-free games and the fact that I like to import games. Their shipping is quick and cheap, blowing away the competition for imports.
Overstock.com - This place can't be making much money on it's games. More often then not there is a deal between 10% and 20% off, no tax and cheap shipping.
I know they aren't overly notable for software, but their hardware and accessory offerings (especially for PC gamers) are very good, and they are rock-solid in the dependability category.