Hell no, they're the most valuable properties in the game. Boardwalk more so than Park Place, since there's a "advance to Boardwalk" card in the Chance deck of cards. And since there are only 2 properties in the group (instead of 3 with most of the others), it's easier to build houses/hotels quickly, even at $200/house. (Remember that you have to build houses evenly across properties in the same group.)
The big loser is Dark Green, i.e. Pacific, North Carolina and Pennsylvania Avenues. The properties cost $300-320 each, houses are $200 each, there's three of them, and they're the least frequently landed-on properties in the game.