Sox are top banana in the town. Its pretty much always been that way. They draw in more casual fans and even the non-sports fan. The bandwagon there has been much larger than either of the Boston winter sports teams. There's a reason the media tends to focus more on them than the other teams in the area; readers, viewers, and listeners are more demanding of it. No matter the outlet, they are driven to what the masses want.
#2 in the town has changed over the years. I think you could make strong cases for the Celtics, Bruins, and Patriots all taking spins at #2. Right now, its gotta be the Pats. Hasn't always been that way, though.