Depends on how fancy or not fancy you're going for, but here goes:
is one of those local places, most of the patrons are Chinese, everyone behind the counter speaks mostly Chinese. They're cheap, have huge portions and awesome food! The menu is in both Chinese and English, it's best to order by number. You walk in, order at the counter, find your table, they'll call your number, you walk back up to the counter to retrieve your food. No fancy decor but AMAZING food!
Is fancier, not too expensive; I've had dim sum there for 11 years, had my rehearsal dinner there, take my daughter there for her birthday dimsums, am planning a huge family reunion there next summer. Pink/Red/Gold gaudiness, but the food is great. More of a traditional restaurant: wait for your seat (two huge dining rooms and there can still be a wait), order at the table, etc. Dimsum is different service (wait for seat/table, order off of the carts, pay at the end) but oh so yummy.
Finally, Eldo Cake House
Mostly I order their baked Cha Sui Bao, baked bbq pork buns, cheap at under a dollar each, the best in Boston's Chinatown, imho. I order two dozen every Christmas for my non-Chinese family. They love them! But try anything from their cake, pastry, bun case. A hangout for the old folk, so I normally grab my snacks to go.