what can I say, I'm a born instigator... I think Rumney is so popular a) because of Ken Nichols, b) because it is very close to 93, and c) climbers tend to have a herd mentality.
There are in fact a handful of other sport crags that easily stack up against any single crag at Rumney: Shagg, Wild River, Sundown, the Laughing Lion. Most of them are even in a guidebook. None of these places have the moderates, however, and they are each a slightly longer drive from Boston.
This may sound funny coming from me, but I think New England (especially southern NE) desperately needs more sport crags. For years Ken made that impossible, and the development was focused almost exclusively north of Massachusetts. I'm not saying we need to retro-bolt anything, but I'll bet there are still undeveloped crags lingering in the surburbs that would yield enough good sport climbing that people would have more options other than driving two hours every weekend to go to Rumney.
Since I'm in a magnanimous mood, I'll even offer up one such locale: There's a great little cliff in Durham, CT, where I grew up. Bear Rock, it's locally known. I used to top rope and boulder there as a kid, I believe only one line has been bolted, but I bet it would yield 8 - 12 routes, similar to Bonzai, and a few properly hard lines as well. Some one with a bristle gun get out there and make the masses happy!