This is a very interesting topic, as this varies at almost every hotel. I travel a lot, most weekends during the winter, and I am sometimes amazed by how little some hotels offer, compared to others.
I was in Fairfax, VA in March, and we stayed at a brand-new Holiday Inn Express. It outfitted all of its rooms with new HDTVs, and you'd expect it to have a full cable line-up. However, the system had only around 20 channels, with no My20 (which meant no ACC tournament), no Comcast SportsNet, no MASN, no ESPN2 (I believe), and I don't think we had PBS, either.
Generally, when you go to a smaller town, they are more likely to have a larger cable lineup. I stayed in one recently in Emporia, VA that had the entire Comcast lineup.
Also, the hotels in Athens, GA are usually good with it, as you get almost all of the Charter lineup on those systems. In Chicago, I have never gotten WTTW there, because at one of the hotels we stayed at, they put the DirecTV basics channel over PBS.
Still, many hotels are stuck in long-term contracts with LodgeNet that they signed late in the 1990s and early this decade, with Nintendo 64

games, and the On Demand features which are years behind what you get even with Comcast. They say they have the sports packages from DirecTV, but I haven't seen a hotel that has any of those packages.