Football ratings will always be higher, in part because there's only one game per week. However, the most popular team in town is, by far, the Sox.
I am not so sure about that anymore. I think they are the most well known, but their popularity has taken hit over the last few years. The interest just is not what it used to be.
Ultimately, I think this is a nearly impossible question to answer right now, since there are so many variables. I think it's pretty cut and dry that there are two groups. The Sox and Pats, and the C's and B's. But I don't think it is cut and try how to rank them within those pairs.
If we are talking about this year, 2010, I would probably put it at Pats, Sox, C's, Bruins. The Sox have lost a lot of momentum, and a lot of factors have led to people simply not really caring about this season with them, while the Pats have a lot of interest, because they are kind of underdogs again. And of course the C's made it to the finals, and signed Shaq which keeps them above the Bruins...but if Seguin shows well next year, and the C's stumble at all, the B's (who have just as strong, if not a stronger loyal fan base as the C's) could leapfrog the C's.
I think it is going to be very tough to break up the two groups at this point. The B's and C's have fallen so far behind in the last 15-20 years, that its just going to be tough to get in that top group again anytime soon. But within those two groups, I think there is a lot of leapfrogging depending on how each team is doing at any particular time, what part of the season it is, and the overall personality of that particular team.