I love empire building strategy games (I think it really taps in to my megalomania). My current favorite is Crusader Kings II and it is hard to say which is my all time favorite but I think it would be a three way tie with Imperialism, Alpha centauri, and Hearts of Iron 2.

Gotta say the original Civilization or Civ II. Just incredible games.

Never played the old Civs, but Civilization 5 is my favorite empire building game.

Pharaoh if it counts, followed by Hearts of Iron II.

I think my all time favorite is Age of Empires II (cliché, I know.... ;p)

Love them all myself, Total war, civ series, sins of a solar empire, tropico and grand ages:rome to name a few

Civ4. Most complex game of the series. I also like EU3 a lot, but turn-based is more my thing.

Same here. I just get overwhelmed in RTS games. Me no have fast enough reflexes.

Rise of Nations & Stronghold: Crusader if that counts

Master of Orion 2. There's nothing as satisfying as bombarding an entire planet, and killing millions :D

This...

or rather:

There's nothing as satisfying as bombarding an entire planet, and destroying it afterwards with the death ray just for the "lols".
Mounted on a doom star while listening to your mp3 player - obviously - playing the Imperial March theme.
Oh and eventually reforming the planet's debris into a new planet to colonize with the "Artificial Planet" research.

I was a big fan of the Rome total war. I have not clicked with the other ones the way I clicked with that one. I hope TW Rome 2 is good

I have to agree with Licurg :) MOO2 rocks.

And now on OS X too! I'll be able to play in on my MacBook Air in bed :D

Rise of Nations, CIV IV (just got Civ 5) and Mount & Blade Warband

really need to dive into the genre more though