It really bothers me that people consider games like Starcraft 1/2 to be superior to a next generation RTS such as World In Conflict/Company of Heroes. Starcraft 1 was a great game when it came out in 1998, but when people keep saying shit like "Starcraft is the best RTS" I facepalm.
Really? A game with basic RTS mechanics (though it lacked que-build back in the day) is superior to 3d graphics, complex combat, and tactical depth? I really like Age of Empires 2, classic RTS, but do you know what? It isn't as good as Homeworld 2 (I have heard the first one is better) or Opposing Fronts, I know difference between nostalgia and game that is still good.
On the other end of the spectrum we have games like Stronghold: Crusader and Battlezone, games that perfected a niche (and would eventually have inferior sequels) and have yet to be de-throned. The difference between these games is that the former no longer can claim originality in their gameplay, while the latter can. Battlezone has a completely functional and easy-to-use system that combines RTS and TPS gameplay, with Stronghold having a castle sim and RTS hybrid that keeps it from bogging down and becoming stale.
You need to do new shit if you want to stay fresh, and you need to perfect something to stay superior in the future; or else it becomes a game that lives on nostalgia.