The success of the Charger has absolutely nothing to do with being RWD. Nothing at all. When it was released, it was well hyped for being the rebirth of the Charger name, and the base model sold for about $22k. That's dirt cheap for a car that big. That really low price also meant that the "urban" consumer could now have more money available for 25" chrome spinners. It is ridiculous how many base model Chargers I see around here every day with huge tacky rims on them. Probably less than a quarter are R/T models, and the SRT8 is a rare sight.
The G8 was a vastly superior car to the Charger, and though it sold decently, it didn't exactly save Pontiac. The fact that the base model started over $27k had a lot to do with that, and except for 50cent, no one in the black community gave a crap about it because it wasn't designed to fit huge wheels on it and even if it could, they couldn't afford the wheels after buying the car.
RWD is not a mass market feature, especially in the sedan market. The average consumer doesn't care about it, as it provides no benefit to the average family when going to the grocery store or taking junior to his little league game. For the average consumer looking for a sedan, FWD is simply a better option.