Yeah...Starcraft is mainstream RTS. It capitalizes on combat tactics and not much else.

Stronghold is definitely worth a look: Strongold 1 and Crusader were great. Unfortunately, they keep seeing worse and worse additions to the franchise. Stronghold focuses on castles in the Middle Ages. There is an emphasis on some warfare, but it largely focuses on castle life. Also, it has by far the best base-building mechanics of any game I've ever played. You construct your towers and walls and station your troops on top of them to fend off enemy siege towers and ladders during sieges.

Age of Empires is good. Have you checked out the Online edition of the game? Age of Empires Online doesn't quite live up to the graphics of Age of Empires III or even the ingenuity of Age of Kings, but it's still a free to play RTS game that specializes in multiplayer. You have a home city that you build yourself, upgrade your units with equipment and research, and create a unique and diverse playing experience through a series of mission that span across the Mediterranean. 

Company of Heroes, as someone said, is the most beautiful of the RTS's right now. It makes use of a cover system like Dawn of War did. Environments are totally destructible, so the tank that your riflemen were hiding behind can be completely blown to pieces, and your riflemen could still use that tank's smoldering frame for cover for pretty much the duration of the game. It's very realistic, but if I can tell anything from your likes and tastes, you're going to be more into the medieval RTS's.

I'd say that Stronghold is probably the game you'll like the most. There will be another Stronghold game, and the studios that makes it won't be pressed for a release date this time, so it should be much better. What's more, it's Crusader 2, and Stronghold Crusader was incredibly addictive and still is. If they took Crusader and slapped new-age graphics on it, I'd buy it in a second.