Games RTS style like Warcraft 3, as in build a base and attack your neighbors:
Command and Conquer series
Age of Empires/Mythologies
Empire earth 1 and 2
Rise of Nations
Rise of Nations: Rise of Legends
Dark Reign 1 and 2 (though 2 is way better)
Metal Fatigue
Ground Control 1 and 2
Total Annihilation and TA: Kingdoms
Supreme Commander 1 and 2
The list goes on. There are literally hundreds of games in this genre that play like W3.
For the person who said X-COM...I'm not even sure how you made that connection. It's not an RTS, if anything, it's a Turn-based strategy. Still my favorite game though.
There are other styles of RTS, as some have mentioned; Dawn of War 1 and 2, Company of Heroes, Jagged Alliance 1/2/3. These are more about your individual units instead of mass armies, and the missions are more covert than swarm-the-enemy types.
And then, of course, branching from there you can hit the 4X space games...don't even get me started.