IMHO there aren't many sop players that can get anywhere near Peter Roberts. What i'm surprised at is that I don't think anyone has yet mentioned Steve Barnsley (BAYV). He's the only one who could get anywhere near him.
I have found that there is no "One" great sop player around at the moment. Roberts is up there, so is the BAYV bloke, Alex Kerwin, Nigel Fielding, Kevin Crockford and a few others.
These different players do different things really well. No one player is head and shoulders above the rest. It also helps if you have a great band to play with when you are on sop. You can just sit on top of it and it almost makes it easy.
If your band is playing well then it is easy to sound good. You can have moments of individual brilliance but in the whole scheme of things, it is how well you play with a band and all of these top tier players do that very well. They are all an inspiration to me.