Graphics actually have held up modestly well, due, I think, to the colorful and less... what we now call "gritty." Putting that aside, though:
I still enjoy MOO2's non-standard take on research (In that, most races will research towards a broad category, such as Communications, and usually be presented with 3 different technologies. 1 they will recieve, and the others will have to be stolen or traded for). There are exceptions, with a trait that allows you to recieve all three (or however many) picks, and another that (If I recall correctly, I never used it) chose 1 breakthrough for you. This would lead to some interesting choices, like choosing Soil Enrichment, for some extra food production, or Habitation thingy-whatsits for greater population on your worlds (which you will need more food to sustain!)
If you have ever played MoM, the population management is identical aside from the ability to move colonists from one planet to another, or set them, in addition to farming and mining, to research. (Edit: I forgot to mention that if you took the effort to invade enemy planets rather than simply bombard them to dust, that those conquered colonists are yours to do what you will with, complete with their race's specific bonuses and drawbacks. Sometimes this will give you an added boost in an area you needed it).
In the same vein, I find races in MOO2 to have more personality than in GalCiv, no disrespect intended. This is in part to the more powerful positive and negative traits, which have a far greater impact on the game than their counterparts in GalCiv. Psilons are the research powerhouses, and will very rarely place even second in research points (barring custome races using the same traits) and Klakons are so focused on production and are so prolific that they will give those superior Psilon ships a run for their money in numbers alone. Gnolams, the lucky race, really are lucky. They're constantly the target of random beneficial events that other races would love to get their hands on. And the Cyborg and Silicoid races, able to eat some or purely minerals, allow them to thrive on worlds that other races would be placing on the bottom of their list.
These races just had so many (pretty well balanced, if powerful) traits to choose from, that had real immediately tangible effects, that it's hard not to feel a strong erge to attribute personality to them.
The Antares side story is a nice addition, with the increasingly hostile random attacks. It's hectic discovering you have a massively powerful and hostile fleet from another dimension inbound to a major planet of yours with an ETA of only 4 turns. Do you pull the colonists off, or can you raise and reroute enough forces to stop them? Thankfully, though, those attacks can be disabled at game creation for a more traditional 4x game.
The games tend to be shorter than in GalCiv, reaching end-game levels of technology only on the largest maps, or on amazingly peaceful smaller ones. But I tend to play on the largest maps possible, whatever the game 
Exploration is more important, in a way, as planets are fewer in number, and tend to range at the lower end of the hability spectrum. The planets also have a bit more... personality, if you don't mind me... personifying a planet. See what I wrote about race traits, and apply that to planets. The Bonuses just mean more to the game and to your empire. Even large maps will only have a few seeded Terran like (or better) worlds, and even fewer will be unguarded by giant space eels or the Guardian.
Space combat is..... infinitly more fulfilling than GalCiv, if for no other reason than you have control over your ships. Different weapons have different effects, like turning enemy ships, which might have some of their weapon mounts facing the wrong way. Combat is turn based.
Ship design is less powerful visualy than GalCiv, which is no surprise, as no one comes remotely close in ANY genre. You get a few set sprites you can choose from per size class, and based on race. Internally, though, the customization is more robust and varied than in GalCiv. You have numerous more-or-less unique weapons to choose from, and each can have various customizations that will effect things such as range, rate-of-fire, accuracy, etc, at the cost of... well, cost, and available space within the hull. There are also varies extras, like medical bays, or ship-based research labratories, that allow for more specialized ships.
Leaders is an area where you see a big detour from the standard 4x model. You can hire the services or random captains and governors, who each have their own abilities. Governors may be attatched to a solar system, and will increase that solar system's production of minerals, or taxes, or farming, or research or lower the polution produced by the industry. They also have more abstract abilities, like increasing the effectiveness of your spies. Captains may be assigned to single ships, where they will have effects such as increasing that ship's accuracy, or allowing it to make minor repairs during battle.
Both types of leaders are unique and few in number, so it's important to pay for their services when you get the chance. They also gain levels as turns go by, which increases the potency of their abilities, and makes their loss, whether through combat or a sudden lack of credits, that much harder to face.
Unless you have two older PCs with serial ports, Hotseat is your only chance at multiplayer, but the AI isn't bad in its own right.
I've tried to be concise here, but MOO2 is one of my favorite games, and I tend to ramble. I heartily suggest getting it.
