The boys at Toys R Us have Sonic Generations for pre-order, for the low price of $37.49. That is pretty damn cheap. The issue here is that its not available in stores and is only online. But they ship your item for free.
Another issue is that the Casino Night pinball stage is exclusive to Gamestop pre-orders. That means that you will most likely have to wait for that DLC to hit PSN/XBLA for a price. But if you don’t care, this is an excellent price.