I've played a lot of RTS games and a few slower paced variants over the years. Fell in love with the genre with command & conquer. Here's the list of games I remember the most.
Command & Conquer series with the exception of the 4th tiberian installment.
Civilization: Call to Power, Civ IV, V.
StarCraft, WarCraft II, III.
Rise of Nations
Heroes of Might and Magic III, IV, V.
Dawn of War I, II.
And my all time favorite because it was done so well:
Company of Heroes. If you haven't played it give it a shot. Game was released in 2006 but the graphics still hold up well and it's an incredible experience online. This is coming from someone who suffers massive anxiety attacks from doing RTS multiplayer. (As a side note, does anyone know why?) Vehicles will suffer realistic damage from hits made to specific areas, most of the environment is destructible, unit placement is important due to things like stone walls and craters providing cover, and a neat system of special powers to choose from as you do better in the match/campaign.