Turn on Mega Events.

Don't thank me yet.

Also, consider increasing your difficulty level.

The weakness Matthew pointed out is common to most (maybe all) strategy games: Before actually winning the game, there is a phase in which you surpassed the AI opponents in most or all areas, so your victory is basically assured and the act of achieving it is just kind of a formality. Since this is a weakness of the genre in general rather than GalCiv in particular, it´s nothing that "needs" to be fixed, but it would, of course, improve upon the gaming experience.

At first glanze, I see two ways to deal with it:

1. Behind-the-scenes adjustments: Modern racing games often employ a kind of rubber-band system, that slows down AI opponents which are far ahead, and speeds up those who are far behind. Basically, the same could be done in GalCiv: opponents which are far superior to the player receive a malus to their economy, research, production etc. to allow the player to catch up, while those who are much weaker than the player receive a bonus. This way, the balance of power among player and AI races could be improved, and the game would be challenging throughout the entire match.
   
2. Visible adjustments: Aside from giving the AI opponent hidden bonuses, the AI opponents themselves could be improved by implementing scripts that allow them to recognize the players superiority and find ways to undermine it. There are already some minor scripts of that kind in GalCivII, for example the AI refuses to trade weapon techs to players that have a strong militia. More radical scripts could, for example, have the AI form big alliances of 3 or more races all allied to each other to defend against the threat presented by the players superiority. Or they could have weak races who don´t stand a chance on their own surrender to stronger allies, to create a force that can oppose the powerful player. There are a lot of minor and major scripts that could be used here.
   

The advantage of the first approach is, it should be rather easy to implement and I think it would be quite effective. The AI would be kind of cheating, though. The advantage of the second approach is, that it´s visible to the player, making the game more interesting, and giving the late game a unique feel. It´s more difficult and time-consuming to implement, though, and might not be as effective.

One final note: something you must never do is "hurt" the player in response to his success (like in Matthews band of raging pirates idea). In a game, the player must always be rewarded for doing something well, not punished. Otherwise you risk hurting the players enjoyable gaming experience and motivation. Of course, if the player won´t realize the connection between his success and the bad things that happen to him it´s fine. So things like the pirates idea can still work, but you have to use them carefully and economically.

Anyway, the focus must always be on strengthening the AI opponents, not on weakening the player.

In WWI, the German people were convinced by the media that they were winning the war, right up till the day before Armistice.   Interesting trivia fact.

The only real option is to prolong the inevitable, whether it be a win or a loss. The end result is always going to be the same, it's getting there that's the problem.

Do you create more in the way of micro management to prolong the news? Having to be more involved, make more choices would allow for greater flexability in the outcome...

Do you create a tactical combat module to allow for more than the gun for gun and your done for battles? Maybe that one ship doesn't survive just because it's got more guns or shields. Maybe evry enemy ship targets the shields in one massive concerted burst and overloads the shield generator or the power generator leaving the ship defenseless. Allowing for tactical genius is what makes chess the game it is, and it's far less complex than GC2. As it is, battles are really more like checkers...

Do you create a penalty for growing too large or too advanced? Opulant and exotic have their price... The latest incarnation has the first glimpse of that in the huge cost increase of higher weapons techs. The same should be done for all buildings, ships and starbases. Maintenance should increase as your empire grows, as well as money lost to corruption and waste. Maybe there's a point at which you really need to stop building ala CIV4.

Do you create more varied weapons and defenses, making some not accessable to all races? Do you make minimal defenses available for some of them? Is it possible to do so without severly unbalancing the game?

Me personally, Tactical combat would be the most welcome addition even in a simplified form. So long as you have the ability to outsmart and outmaneuver an opponent, to use cunning instead of force, especially if your a tad inferior tech wise. That would make things a little more interesting. Throw in a corruption/maintenence scheme and it may be you simply can't take over the whole galaxy...

T