In GalCiv II, you have 6 types of buildings - research, production, food, entertainment, culture, money. All the improvements are just upgrades. In GalCiv I you have more diversity. Fusion Power Plant, Anti-matter Plant, Bank, Exchange, etc. Accomplishes the same but less cookie cutter.
I actually felt more limited on the planet construction with GalCiv II. It felt more restricted and cookie cutter than GalCiv I
The tech in Gal Civ II is specific to a need. You need A, you resarch tech 1. In Gal Civ I, the tech is more natural. Galciv II also felt more cookie cutter on the research.
Gal Civ II has some great features like letting the tech overruns be carred forward to the next tech, anomalties showing up on the screen, but overall it felt less fun.
The graphcis was insteresting. Galciv II looked great and I was OK playing, yet when I went back to Galciv I, the refief I felt because the 2D srceen was in a clear 2D format was interesting. Its still 2D in Galciv II just camoflauged to look 3D and then your brain has to do the conversion. So I was more relaxed playing the simple 2D of Galciv I,then decoding the psuedo 3D of GalCiv II.
I played Galciv II for a couple of months and enjoyed it. Then decicded to play a game of Galciv I for old times. That's when it hit me - I like Galciv I better because it was more fun.