Usually if it's anything more than 75 daily seats or so, I'll send a 737 in seven times a week. However, at DAL and ones with shorter runways, I usually run the CV-440 in older game worlds, as it has lower fuel consumption. Replacing them, however, is near impossible to do with another prop until the ATR-42/72-600--since the range on any prop is much lower than the (I believe) around 1,200 mi range of the -440. Usually I end up splitting it between an RJ and a newer turboprop like a Saab 2000 or Q-series. Since DAL has seat restrictions you're pretty much forced to use a smaller plane with higher frequencies.
Although it isn't very realistic you can run the AN-72 to pretty much any destination in North America in a 56 seat configuration. It has max payload range of 1937 and a max fuel range of 2980! It is a bit slower (437 vs. 505) than the CRJ-700 which comes 15 years later but fuel burn is the same. Fuel consumption of the AN-72 is quite a bit higher (5x) than the contemporary Q300 but the speed is 50% higher mitigating that to a certain degree.