What similarities exactly?

The interface the way the game plays out the It's all very similar. Quite Boring really.

You need to go into more detail than that, because I'm not seeing it at all.

As for similar gameplay, you could say this about every other space 4X game too. They all play relatively similar to each other.

The interface is nearly identical between both games

It always kind of reminded me of STARS! but then everything does.

Doom reminds me of STARS!

That reminds me, I need to reinstall it

Even stars remind you of STARS! =P

Well yeah, duh. :P

Seriously GC was to me always like STARS! with the look of Space Rangers. Fortunately I love both of those games so I'm good.

I can see some similarities in the main map, but that is the case with most games of that kind. Other than that, I have to disagree.

Okay then.

Since I'm definitely tempted, but I'm not totally sure I want to ask as someone who loves both MoOs - "They made a third one? Surely your imagination must be running wild." - would I like this? What can I expect to be different? Am I recalling correctly that fights actually happen on the star map versus tactical screens in MoO?

Yes, I'm still hoping for GalCiv 2 here, but I've played that so long ago and so little of it I have very little memory of it, so I suppose I wouldn't be missing anything if I played (and maybe enjoyed?) its prequel.

In my opinion, If you will like GalCiv depends primarily on if you want tactical combat or not.

If yes, then you should be prepared to be disappointed, because combat is abstracted in GalCiv. It is very similar to Civ in that regard. There is also no ship customisation and orbital bombardment. Still, there are Terror Stars, which are star-system-destroying starbases. Plus, you can fit out your starbases with modules that enhance the combat-effectiveness of all your ships in the same star-system.

The other two major differences, in my opinion, are the AI, and the customisation (compared to MoO 2):

The AI in GalCiv is pretty good, especially when compared to other 4X games of the same age. Unlike in most games, this AI actually knows how to play. It doesn't cheat, unless you play on Painful or higher, and even then it only gets more money and some ability bonuses.

The customisation in GalCiv is somewhat lacking, due to the main focus on the AI. What customisation is there, is mostly statistics (e.g., +10% research, or +20% faster population growth). None of the fun choices, (like, for example, High Gravity and Telepathic), that MoO 2 had. You can also only play the Terrans in GalCiv 1.

One thing I absolutely love in this game is, that the other races feel "real", for lack of a better word. They have a history behind them, and this comes across during your interaction with them (and it only got better in GalCiv 2). This is something I never felt when playing either MoO game. I couldn't tell you anything about the Sakkra or Meklar, except for what their statistics say, but I know exactly who the Drengin and Altarians are.

Twelve fully playable races, all with their own tech tree. The ability to make your own races. The ability to further customise your enemies. Super Abilities. Mega Events (game-changing random events). More diplomatic options. The ability the mine the resources of asteroids. A better tech-screen. Extreme planets (aquatic, barren, heavy gravity, radioactive, toxic). A ship designer (customise both the look and the equipment of your ships). An even better AI. Fleet battles (put your ships in a fleet, instead of sending them one by one against your enemies). Multiple damage-types (beam, mass driver, missiles) instead of one. An overhauled colony screen (a bit closer to Ascendancy, if you know that game). Much better UI. Tourism-income. A new espionage-system. And so on...

Yes, you wouldn't miss anything. ;p