1. Command & Conquer series - Sure I may not like EA very much, but at least all the games are good except the C&C 4. Despite what they said, Generals is a good game, it is just people think it don't deserve a C&C name on it.
2. Starcraft - Boring but addicting type.
3. Age of Empires - Unique gameplay, the pioneer of the multi resources game. As good as advertised, too bad Ensemble closed down so we probably won't be seeing Age of Empires 4 anytime soon.
Warhammer is #1 for me. Dawn of War 2 was one of my favorite RTSes of all time, and Dawn of War 1 was pretty stellar in its own right.
Warcraft is #2. It was close with Warhammer. Warcraft 2 was one of the first RTSes I ever played, and the first I ever played online (via Heat, I think). Warcraft 3 is, imo, Blizzard's best RTS.
Sins of a Solar Empire, #3. A 4x-lite, with huge, epic battles.
Supreme Command is #4. Huge scale, and a large variety of tactics and strategies are available. More options than a lot of competing games.
Honorable Mention: "Other"- Warlords Battlecry series. I spent a ton of time in all three games, growing up. Never played much multiplayer, just the skirmish mode and the campaign. Pity the AI was so terrible.
Other poll options: -Command & Conquer, never really played them much, never really got into them. -Age of Empires, I played them a lot when I was younger, but they never quite left the same impression on me as other games. -Starcraft, SC1 was great for its time, but doesn't hold up as well these days. I found SC2 to be a pretty huge disappointment, with its focus on e-sports, and its lack of innovation or genre-advancement. It was SC1 slightly refined, and that's not what I was looking for anymore. -Battle for Middle Earth, never played it. -Company of Heroes is objectively one of the best RTSes around, I think, but I just could never get into the WWII setting. I'd definitely love to see more RTSes model themselves after these games though.
The sole purpose of this space is to make my post look longer.