I've always loved the game comparison arguments. They rate up with with Mac vs. PC and PC vs. Console. Tastes are so remarkably different between people it's almost impossible to actually pick a 'game of the year'.
As an example, take this year. Assuming Doom 3 and Half-Life 2 actually come out this year, and are decent, I'm willing to bet one of those is going to be this year's 'Game of the Year'. Unfortunately for me, I hate first person shooters, so... I guess I'm just out of luck this year.
Back on topic, however, as was previously stated, Freelancer was more arcade than space simulator. X2 was a hybrid economy space simulator. UC is more like putting you in the seat of the President, only able to actually join your different military divisions in general combat if you wished. Much more tactically oriented and complex.
Which is the best game? Depends on who you ask and what they like. However, I'm pretty sure a lot of people will say this:
Freelancer was fantastic... for the five - eight hours the story ran for. Then it just sort of ended and left you hanging with no real rhyme or reason to continue. The ships don't have advantages or disadvantages except for getting 'better' as you get to different systems, so if you did have the urge to play after you beat it, it would soon end. Average life for Freelancer is about or less than a week.
X2 is hard to pin down. I value my life and my time seems to be too expensive to invest in this game (same with MMORPGs). If you can tolerate the long wait times, and get a kick out of slowly building yourself up to the end all trading guru leader of the galaxy, you might be interested. Overall it seems like a lot of people try it, but it falls into the category of too much effort with little payback. Average life would be about a week before most give up. If you stick with it, could be months of sheer space trading excitement.
Then you have something like Battlecruiser/UC. It has a lot of stuff to do. It has a lot of options to be. Just about every aspect of feeling like you are in command of a capable, able space-going army is available to you. Because of this, it is obvious that there will be a steep learning curve. It may shy away the casual gamer, but this game has never (to my knowledge), been claimed as 'a game for the casual teenager one day after school'. That's one of the interesting points about the UC series, is that it knows what it is and who it is targetted for. If you take that into account, those who like it will be addicted. Those who generally do not, it wasn't designed for them anyhow.
A lot of games these days are starting to forget what exactly they are. RPG's where twitch action is required. First person shooters where you have to get your skills before you can shoot that rocket launcher. Adventure games trying to be interactive books with pointless arcade elements needlessly thrown into the mix. This is part of the reason why I always find it amusing when some magazine or webpage can claim a 'game of the year', since it is not possible. One of the elements for a 'game of the year' should be that the game knows what it is, and it hits that genre. It doesn't try to blur the lines (which is why I don't like KOToR being selected as a game of the year, for example, not that it was a bad game, it just didn't know what it wanted to be).
If this was a requirement to selecting a game of the year, then you would have UC up against the likes of Doom 3 and Half-Life 2, assuming they are just FPS types and don't try to play games with my head and be a pseudo-RPG.
Once again back to the topic:
If you like space invaders, you may love Freelancer.
If you like playing Monopoly: Star Wars Edition for hours on end, you may find X2 to be a new form of sheer excitement.
If you like... BC3K... you'll love UC. This series has always been it's own virtual category and likely will always continue to be, so there is nothing in existance to even compare it to.
I hope nobody minds long posts, because I like to make sure I state my point as clearly and completely as possible. This being my first, inspiring post, I bid everybody who reads this a fine hello and what not.