i live in south cali, and the blockbusters here are also decreasing in gamecube games. but, we have another chain close by called hollywood video. there may be one by you, i dont know how far the store chain goes. they are picking up on blockbusters slack and have a pretty large gamecube selection. it almost rivals the PS2 section, which is about 2 rows long. they also sell just about every gamecube game made, and its where i buy all of mine. and most of the guys that work there are major nintendo fanboys, so they try to limit X-box's shelf space as much as possible.
i dont know if the other stores are also like this, but the one by me is. you guys would love the place.