I never got into it before now because at first glance, the galciv games look simplistic next to flashier 4X games like Sots and Sins. Square grid? Auto battle resolution by RNG? No real difference between the three weapons classes?

But as I've been playing, I can see how it has better longetivity, partly because it is a deeper game than it appears, but primarily because of its superior AI. Sins' AI compared to this one is a fairly dull-witted 12 year old, and Sots' AI is a drooling drugged-up monkey randomly mashing at the keyboard. If one doesn't have friends who play 4X games, then a good AI is the most important aspect of any strategy game.

My first game, I played against a few sub-normal AIs and rolled them handily. That was to be expected; I was learning the game. The next game, I put in a bunch of tough AIs (it's cool that the even-steven, non-cheating AI is called "tough" as opposed to being the second-to-easiest difficulty) along with the Drengin at Genius. It was sad how bad I got crushed. He picked off one opponent at a time, letting me linger across the map until the other, stronger players were finished. I thought I had a chance to somehow come back at one point, but then the Altarians surrendered to the Drengin (even stating "I trust the Drengin will take good care of my people," OMG I laughed out loud) at which point my poor Torians had a one-way ticket back to slavery. I even tried bribing him for peace and setting up Ascension bases, but then Lord Kona asked if I really thought he wouldn't notice before the final onslaught began.

My current game has me as the Korx vs a bunch of tough AIs on a large map, and the Drengin returning one step lower as Gifted, which has only a minor economy bonus of like 10% or something. Even so, the Drengin are #1 in most of the rankings mid-game, and I keep them in check only by bribing the other AIs to attack them. (I was lucky enough to start across from the map from them.) But a final showdown is inevitable, so I'm researching up military tech while I finish mopping up the Altarians, Yor and Torians (the latter whom I made sub-normal as punishment for their failure last game). Maybe with their planets, along with the Terrans as allies, we can finally beat my nemesis Lord Kona. It really could go either way, and depends on my economy/tech surviving his massive amarda If it were a Sins or Sots AI with only a +10% cheat, the game would have been over long ago.

tl;dr: AI > * in a 4X game's quality for a solo player