I'm kinda stuck on this. It's outshone by the cleric and even wizard, who can do other stuff on top of Necromancy easy. Do the brilliant gameologests have anything on this?
What are you looking for, exactly?
The cleric is good at making undead earlier than other classes, and they get access to Desecrate. Also, they're clerics, which makes them awesome in other ways.
The wizard is good with negative levels, and you can do some cool stuff with certain metamagic feats. Also, they're wizards, which makes them awesome in other ways.
The dread necromancer is good at controlling a lot
of undead at a time. That's really the only thing they have on top of the other classes. That, and they have some interesting familiar choices. So, if you can find a way to get Desecrate on your spell list and pull some metamagic shenanigans on Enervation, you'll start to pick up some of the necromancy tricks of the other classes. Also, pick wisely on your Advanced Learning spells. PrCing into different classes can also widen your spell list.
Beyond that, I'm not sure what you mean exactly by "best necromancer".
Also, have you read K's Revised Necromancy Handbook
? I'm not sure if it's ported over here or not. I've heard some things are out of date, but it has some good info overall.