Mass is far from the worst, overall. Far from the best, too.
DC doesn't count, as it's not a state. if it was, it would be the worst on the planet.
Handgun wise, Illinois is the worst, hands down. Rifle wise, it's up with the best. Why? No CCW and no AWB makes it that mixed bag.
Vermont is arguably the best. No CCW required, no AWB. Only thing the Feds allow that the state doesn't is silencers. That's a Fish and Game issue up here. Funny thing is, NVD's (night vision devives) are legal.
Alaska is next. Pretty much the same story as VT. They have optional CCW permits, which I wish VT had. I hold 2 NR CCW permits (NH and UT), so I can carry most places.
The PDRK is the worst rifle wise, PERIOD. Add the iffy CCW standards, and I'd say it's the worst in the country, if you look at the whole thing.
As to Mass and the number of shops, you should check out Texas, specifically El Paso. I lived there 2 years in the late '70's. I went back on a business trip a few years ago, and went looking around. Well, I think I found 1 true gun shop and a couple of local sporting goods shops (same chain) that carried firearms. I'm sure the big box stores that carry them had them, but these days, that's only Wal-Mart and not all of them. Considering the population of El Paso is about the same as the population of VT, and we've got a BUNCH of shops, I'd say it's a sad state of affairs. Think of Mass having only 10 gun shops for the whole state.