Amazing strategy game that's deep and immersive; a little bit better than Civ4 in my opinion
1. While both games have amazing graphics, Gal Civ II does not require an Alienware computer to play. If you have an average pc like me, you'll probably find yourself playing GC2 more than Civ4 simply because there's a lot less lagging.
2. While Civ4 gives you, "oh, this is such a great game", the first 10 minutes you play the game, it gets repetitive and boring after a while. But Gal Civ II's gameplay just gets more and more amazing the more you play. Simply because there are many ways to win, and it's actually fun to win by a peace/tech/influence victory.
3. As far as how battle works in turn-based games, it's the same with Civ4 and GalCiv2--you click on a unit and click it on your enemy unit, and the battle instantly resolves, just like that. However, Gal Civ 2 is better because you can design your own units and make them prettier.
4. Multiplayer has never been an issue with turn-based games, since 90% of those types of game never use the multiplayer option. In the end, therefore, it comes down to the AI. I think you already has a good idea about GC2 having the best AI in strategy gaming. Besides, let me just say something that the Gamespot reviewer hasn't touched on. Gal Civ 2's AI are all designed with their own personalities, war tactics, and such. You go to the Civ4 forum and post, "I hate the Romans", and no one will have any idea why you do. But if you go to Gal Civ2 forum and post, "I hate the Terran Alliance", believe me, you don't need to explain further.
Go get yourself a copy if you are still thinking!