I think the Soulhunters are in a class of their own. Though it is based on a ship seen in the show, you used that to extrapolate out an entire ship set. Where the Narn/Centauri/Others already had a complete range of ships to use to create a shipset. I actually thought the Soulhunters were well done and have a slightly menacing look to them.
My favorite shipset in the original game is the Amonkrie. The Krill are probably my least favorite - too bland!
My favorite fan set was the Narn and EA sets (from the series catagory), my least favorite are the hodgepodge sets that don't have any cohessive feel to the set (unless that was their goal - a chaotic empire?).
Probably the most creative set I have ever seen was the Lego one
