I work at a electronics dept. in walmart. I would say that it was actually pretty comparable to the halo 3 rush we had, except the halo 3 people were more fanatical. We got a memo from head office saying that every walmart would get at least 100 copies, my store got 180 copies. Still, they were all gone in less then 9 hours.
Milage will vary from store to store, but I'd say it was still a big release. Only recent ones that can compare would be halo 3 and burning crusade of course. Guitar hero had potential to be up there, but Activision is retarded and barely makes any for the wii.
I got my brawl though, picked it during lunch~