Very intersting topic. I agree with pretty much everything you all said. The show would be uninteresting if they were rich because the boys they would be nowhere near as close as they are now. Their personalities would still be the same, but that sense of family-togetherness that you get from watching the show would be gone. The boys would all have separate rooms and Hal and Lois would be out pampering themselves and buying useless stuff like a 10,000 doll house or a steamroller.
They would probalby have a full-time nanny, like Polly, and Lois and Hal wouldn't be as much an influence on the boys lives as they are now.
Malcolm would still be a genius and Reese would still be Reese, but I think they
would probably fit in and be part of the popular crowd. Only it would be because of their wealthy social status, not because the people they hung out with actually liked them for who they are. Most of Francis's storylines wouldn't even exist because I seriously doubt that the spoiled son of a wealthy family would ever be a cook in a greasy kitchen in Alaska, or a stablehand/maintainence man at a ranch. He would still get into trouble, but he'd probably just buy his way out of it. Dewey would be affected in that he would have a lot more material things, but I don't think his actions would be that different, overall, if he had access to a lot of money. I can't see him being a snob or anything like that. I think he would use the money to do things for other people--like he did for Jaime in Morp.