Yeah I really liked Empire at War. A lot of people bag on that game but it's one of my favorite RTS. Yeah the land battles aren't the best but it's cool you can go do the planets and control them.
Well I was one of the ones who was disappointed in EaW because the space battles weren't as good as they could have been, but I love Sins.
I heard Sins is similar to Civ? I have never played Civ. Civ doesn't interest me because I heard the combat is auto resolve and whoever has the biggest army wins. I want to control the army.
Sins is an RTS with some 4X elements. It wanted to capture the scale of turn base games like Civ and total war while having entirely real time gameplay. Combat wise it is almost purely an RTS. In fact it is more of an RTS in my opinion that EaW, since the "game map" and the "battle map" are the exact same thing. There is no transition from one to the other when a battle takes place, you manage your empire while controlling your fleet. Just like in a normal Starcraft RTS you build up your base on the same map you battle with your army, its just this time the map can potentially have over a hundred planets on it. 
In short, the elements Sins takes from Sins are mostly in management, research and economy related, not combat.
What is the best Star Wars mod? I plan to buy the whole Sins on steam.
That depends entirely on what eras you're interested in, how much you want an enjoyable game versus a strict Star Wars experience, and how much weight you give to sticking mainly to the movies versus all of Star Wars canon.
