My "idea" of the mainstream is that they eat up anything with the Star Wars name on it. They couldn't get the Clone Wars cartoons out fast enough (both the animated and the CG? Clone War shows). It also seems that even the most unlikely movies/TV shows make Star Wars references.
I'm pretty sure the box office numbers for all three PT films were great, but I'm certainly not positive about it. I think if GL said that he made a Sequel Trilogy and it was going to open tomorrow, most people (who I personally would label "the mainstream") would be lining up to see it. I saw all three PT movies in the theater. I was excited for phantom menace but not so much for the second two. I remember each movie filling the seats and I even saw my grandparents at Phantom Menace.
Haha, these are exactly the conversations I was trying to avoid (even though clearly I walked right into it on my own). A lot of you could, and should, teach "Star Wars Theory" courses at your local colleges, and while I have often read entire threads and news on fanedits, I have always avoided signing up and speaking for fear of getting flamed for lack of SW knowledge/passion. Obviously this is different because I just put my foot in my mouth today and Alexrd and TheBoost were probably right to call me on it. I try to be Belgium and stay neutral but it doesn't always work out that way. :)