The topic title question asks if FS2 is the best space sim ever. Since no other space sim is as good as FreeSpace2, FS2 becomes the greatest space sim ever.
I agree that some things could have been improved, but out of all games- FS2 is my fave.
P.S. I actually think that if a better space sim was released, then all of HLP would be like the Command and Conquer fanbase: forget the older and better game ( FS2 in this case ) and move onto the new one, replacing the original fans/forum lurkers with those annoying type MP people who expect all games to have the latest graphics.