I started a medium random map (1 star) on single player (locked teams), normal difficulty. After a long hard battle against one AI (up until the end, i was always outmatched in fleet engagements) i finally wiped him out and had total control of half the map with only 2 ways in.
After making a emergency fleet to prepare for a awe inspiring assault by one of the AIs (he had 5 caps and a fleet to match it, the fleet strength indicator was almost maxed out, one system away) which never came, things got real quiet.
I started fully upgrading and building infrastructure on the conquered planets. I got the trade network going, ore processing plants up & running and building new research stations. I then began researching things to improve economy and population size.
I began admiring all the traffic in my little empire and realized I was enjoying the game not as a RTS but as a
empire sim!!! I was building the perfect empire and didn't want to go forth and crush the rest of the solar system.
I've played games like civilization 4 and galactic civ 2 but just lost interest half way though (over a year later i'm still trying to start and finish a map for both). With sins, after the thrill of a brutal war i reverted to empire building with the same amount of joy and without even noticing.
Maybe it's the thought that if Sins and Civ 4 ever came together they would need to add a nuclear winter climate to civ 4, but to me sins has just enough 4x and RTS/RTT blended together so well you never get tired with any of it.
Now i want a empire sim sin mod!!