I have to admit that I missed this game when it first came out since I had an Amiga at the time. Always meant to try it out, but just never got around to it.
I've played Galactic Civilizations II and really enjoyed it. Based on the screen shots, it looks like GC2 is heavily based on MoO.
Anyone here played both and can say how do they compare?

Galactic Civ is actually very similar to MOO2, with some elements tweaked/changed. The original MOO is a bit different due to it's simplicity, and some argue that the extra complexity that MOO2 added actually detracts from the game. I found that Gal Civ 2 was a pretty good clone of MOO2, but not as good as the original IMHO! :)

They're a bit different. GCII has a better diplomacy model and the AI is a fair bit more clever, but it leaves out the ship-customization aspect (functionally, at least; you can still build your own ships but it's more for cosmetic reasons). Both good games.

Always remember that the latter half of GalCiv is Civ. It inherits a lot from Civilization, and so there are a number of ways in which it differs from MOO and MOO2. Ship movement and tactical combat in particular. You will notice parallels, but they are played differently. Great games across the board, though. If you appreciated how smart GalCiv is, you'll appreciate how smart MOO is.

Brad Wardell, The Frogboy, CEO of StarDock said this about Galciv 2 versus MoO2.
"They're quite different but let me focus on the big ones [differences]:
* GalCiv is more about macro management. You're running an entire civilization.
* MOO 2 is more tactics. Your ships go into combat and you control them. Your planets have populations of different species that have pros and cons to them that you can make use of.
* MOO 2 uses star lanes to navigate so you can have natural choke points.
* GalCiv has open space so the focus is on controlling space.
I love both games."
http://forums.sinsofasolarempire.com/378523 complete thread.

I think he's mixing up MoO3 and MoO2 here.
MoO2 has fuel technology that limits how far from one of your colonies or outposts you can fly and you can't change direction of a ship in flight without certain other technologies, but the only thing resembling space lanes would be the worm holes.
MoO3 has starlanes that allow for choke points.

Good catch WK, Someone else noted that in the thread. What he meant I am not sure.

What I assume he meant is travel in MOO2 is more linear between each system. You go direct from one to another, whereupon other fleets can wait for you at the destination point, creating a choke point of sorts. In GC2, you can reach a point by flying around in circles or whatever way you like. You can sidestep enemies if you're quick enough etc etc. You don't have to fly in a direct line/lane to get somewhere. Although if I recall with the right technology in MOO2 you can alter ship's destinations mid journey, travel is still done in a more linear fashion. So even if he has confused MOO2 with MOO3 in the quote, travel is different to some extent between the Master of Orion series and GC2.
Regarding GC2 I was never too impressed by it. I understand it has changed a lot with the expansions and patches but it never had the fun factor of MOO. It seemed slow to get into and when you did experience some action in the space battles, they were non-interactive and lacklustre compared to MOO2's turn based ones. It has a lot more depth if you enjoy large campaigns though, but I'll always prefer the older game.

Me too, and a fair percentage of those who try to play it.

For some reason I ended up liking GalCiv 1 more than 2 (I think perhaps the events brought more color to it), but my real only complaint with either is with bigger games I get Constructor fatigue (get tired of managing constructor flight and use).

Is true Nightshade, I went quite a way through a game in Galciv 1 recently and found it really a return to the game's roots and basic simplicity. Think it has a higher fun factor than 2.
GC2 has ended in Twilight of the Arnor and fans hope for a GC3. But of course Sins of a Solar Empire Trinity is, in many ways, GC3 except not turn based. It would appear that the Sins series is at an end too. The new Stardock game is going to be Elemental: War of Magic.
I am not in the beta, but from reading my impression (correct me if I'm wrong) is that it is going to have about the same relation to Master of Magic as the GC series has to MOO. Just my impression. Might be wrong.

I don't know what it is; I really wanted to like GC2, but I just find myself loosing interest halfway through the game. Part of it, as I said, is Constructor fatigue (but that was a problem with GC1 also) but it just seems to be missing something.
I thought there were some official indications of a GalCiv3 planned, but perhaps I'm misremembering.
That certainly fits what I've heard about it. Of course, there's already a modern game with a pretty strong Master of Magic vibe (though its hard to find): Age of Wonders: Shadow Magic.

Extremely hard to find, and extremely expensive to buy. Extremely easy to find and widely available to pirate.
Sad when that situation occurs. Age of Wonders is an amazing series. I was lucky enough to find them at a used book store for cheap. My favorite game is the first, though :)
Oh and I preordered Elemental and I've been playing the beta for months. It's quite unfinished right now, but the game shows oodles of promise.
It has a wonderful, tactile feel to it. It almost feels like you're playing an RPG. I'd liken it to a hybrid of Heroes of Might and Magic, Master of Magic and Spellforce (if it were turn-based).

I jumped into the Beta as soon as I could (about mid-way through Beta 1) and I would say that Elemental is closer to Master of Magic than GC was to MOO. Not that it's a clone, because there is a number of fresh concepts, but if you enjoy one, you should enjoy the other. Also, since it came up earlier, the customization of the GC series is being carried over to Elemental, but it has a lot more impact on game-play this time around. Equipping your troops with one pair of boots might increase their speed, while another pair will boost their defense, etc. It's more than just: Laser 1, Slightly Smaller Laser 1, Smallest Laser 1, Laser 2, etc. from GalCiv.
As for Age of Wonders: Shadow Magic, I'm up there with Nightshade. It's a great game, but expect to pay a premium for it on eBay or Amazon. It draws a lot of inspiration for MoM, and does a great job.
Since we're already off track here, if you want something with a MoM feel, look up Conquest of Elysium 2 by Ill Winter Design. The devs released it for free recently, and it runs fine on both my 32bit Vista and 64bit 7 machines.
edit: Hmm, they don't link to updated (and free) Conquest of Elysium 2 on their homepage, but you can find it on their publishers site, www.shrapnelgames.com