I have to admit that I bought the game just so I could build Ringworlds and Dyson Spheres. :-)
I also like the incredible depth of play. I made the mistake of buying Imperium Galactica a while back. Pretty graphics but over-simplified gameplay. I wonder if the AI of that game is better though? I still haven't beaten it on medium yet. Granted, the game is so dull compared to this one that I haven't played a second game yet. :-)
Mines, Satellites, Fighters, Troops, Weapon Platforms, the variety of facillities on a planet. The three types of planet types and the different types of atmospheres. All of these make for a game that is loads of fun to play. Plus, the tech tree goes much higher than Master of Orion II.
Unfortunately, that amount of complexity makes designing a good AI tht much more difficult. I know I'm going to dodge rocks for this one. But I think the AI in Master of Orion 2 is more challenging that the AI in SE IV. But again, in a month of owning SE IV, I have already spent more hours of gameplay with SE IV than in four years of playing MOO2. I think it was Baron Munchausen(forgive my horrible spelling) who summarized the difficulties of AI best. We humans learn whereas the AI doesn't. Probably, my feelings about the AI are slanted by the many sleepless hours I have spent playing this game.
I was never hooked on MOO2 like I'm hooked on this game. The Mods. Oh, the Mods are AWESOME. Rambie, if you are ever in Texas, look me up, I'll buy you the biggest steak you ever saw. I love those EA ship designs. The same goes for Mephisto and, I'm gonna have to learn to remember the names of the folks who made the other race mods. (be very embarrassed)
What I'm waiting for right now is the ability to replace all of my races with ones that play as well as the EA, Darloks and Serengeti. Now, that would be truly scary!
Did I say this game rules?