It’s been a long while since I’ve last played X-Wing, TIE Fighter, Elite, Wing Commander, Privateer, Freespace et al. and I’ve missed the genre.
After a little hunting around I’ve found two space sims which look very worth exploring (Allthough, unfortunately, none is multiplayer as far as I can see…):

X3: Reunion is a huge, lovely looking, non-linear Elite replacement. Unfortunately it’s slow, trading is huge and complex and there isn’t much gameplay to keep you going if you want a storyline to follow. The pace is slow, but the detail and possibilities are breathtaking.

DarkStar One is more based on making your money through blowing things up whilst following missions. Trading is an option, but it’s fortunately simple. The graphics are slightly less beautiful but still at times awesome, but there’s apparantly a sameness to the galaxies and trading posts which marrs what would be a top space shoot-em-up.

Both look very worth playing though.