Its funny the rest of the online community is asking for this. I'm sure if these players wanted to decide once and for all who is the best, they would do so one their own terms, and probably free of such public attention. Besides as Cykur mentioned, part of it is just getting warmed up, and at certain levels it can be the decisive factor for who wins.
Being in constant practice and being very familiar with the "flavor of the patch" killer strategy gives players an edge online. The best players probably can't really identify who is the "very best" because it is pretty subjective. Some players are better in some roles or on some types of maps than others. No one wins every game, and people tend to remember the times they beat you while dismissing the times they lost to "bad luck". And besides, many of them don't want to be known as "the best" they just want to smurf the crap out of you.
Personally I feel that overall, based on the most recent performances; Krath has taken the leading edge in the current group of all tier one players. His grasp of the game is 2nd to none right now IMO and his play style continues to be very adaptive. His main strength is that he is very proactive in recognizing developing situations and responds accordingly in an impressively rapid fashion. I draw these inferences because I have watched countless replays of him with JJ, Tyr, Amish, Cykur, and many other notable players to name a few.
Krath is extremely good and certainly a candidate. The 1v1 we played a while back when I returned from a hiatus was an excellent chance to see how Vasari were stacking up against a well played TEC.
I think there are a lot of good players right now. People tend to hold some of the old timers in the highest regard when it comes to skill, but it could just as easily be a more recent arrival who has benefitted from all of the information available on the forums, plays the game constantly, and has mastered the flavor of the month.
The thing is, checking back on this, I don't see many people signing up to play. You can't just nominate the people you think are best and put them in a playoff. Everyone seems to want to see a replay, but where is the line of people who want to play??
I'm with JJ, you would probably have to track stats by CD key to really know what was going on. If there was a benefit to being known as the best, why are their so many smurfs?
ps. I considered JJ my biggest contender when my gaming dropped off back in April. He has played how many games since then?! You does the math.