Now I haven't actually played all the way through or even really played that many RTS games but...
Does Starcraft 2 have the best campaign out of all of them? I really like the meta game upgrades and the choices you get as you progress. It really feels like it's incredibly good compared to most RTS. SC2 does a fantastic job at telling a linear story with linear maps well also letting you have a bit of choice, the only thing I could possibly think that compares to it is x-com but that's a very different kind of game.
For the record the first campaign is entirely free pretty sure so if you haven't played it I highly recommend you give it a go, it's a full game.
