X2 the threat is simply the most epic space simulation of all time. You start off with a single, weak fighter class ship. Throughout the game you fight or trade to pilot freighters, carriers, battleships, stronger fighters, and transports. You can also simultaneously control all of these through the game AI.
Now, this game is far from perfect. Character graphics, while detailed, don't look very good. The combat gameplay is decent, but at release of the game it could use a patch. There are also some minor bugs that cause crashing or corrupted save files. The game is also VERY slow paced; We're talking an Everquest level of time versus reward ratio here.
Still, I've enjoyed this game a heck of a lot better than Freelancer. If you're looking for a rewarding, open gaming experience, this is it.