I don't know anyone who would claim that any MA restaurant could stand up to the major BBQ states -- but, since you asked: Red Bones in Cambridge/Somerville, Firefly's in Marlborough, and Firebox in Bedford are not bad at all.
I can think of three other fine establishments which have closed over the past 20-30 years. Not enough demand, I suppose.
I was thinking about redbones as an option. Blue ribbon just up the road in arlington isn’t bad either though it has been a while since I’ve sampled either.