I dunno, I will admit that my knowledge of the Flames situation isn't as informed as I'd like it to be, so argumentation there is weaker. The downfall of the Thrashers is pretty well documented, though, and I don't think it was anywhere near as simple as "fans just didn't show up". Sure they didn't, but there's always reasons behind that too that we need to look at to get the full picture.
Here's a take in video form that changed what I thought of the city as a hockey market. Make of that what you will, but I think there's some reason in it: