@SmilerLoki, i stand corrected! 
I so liked the scenes with Koringhus I can almost quote them from memory, so no wonder that passage stuck in my head!
I still sont see whybit would matter if Dunyain are closer to Tekne weapons race. Kellhus dispatchex Aurang with ease and Sacarreess couldnt touch Aurang. So it stands that Kellhus is the greatest sorcerer in the world. I also say the smartest moat knowledgeable, which is how he came to be ssmuch a great sorcerer.
The point of that quote is, Dunyain breeding worked, making them more than Men. That was brought up in answer to your question why I think they deserve to be put in a separate category when intellect is concerned.
Thinking about Kellhus and his abilities now, I compare him to other full-blooded and fully-trained Dunyain (because the Mutilated exist, which has bearing on further developments in Earwa). On this my views are as follows: he is in their top 0,2-0,3% by virtue of being a prodigy, but he is not alone in those percentages. This is a realistic outlook on the distribution of talents in a given population, and so I use it as a baseline for the Dunyain population, too. Since we have little information about what other Dunyain do during the events of the series, I consider calling Kellhus the best and smartest premature. I fully expect to get new and exciting revelations precisely about the abilities of other Dunyain (again, because the Mutilated exist). In that regard, my narrative spider-sense is tingling. Additionally of note is the fact that, however it happened, in the confrontation with the Mutilated Kellhus lost.
There is also the matter of the Boy, but he isn't fully-trained, so I expect him to be significantly weaker than the Mutilated or Kellhus. Though I'm not objecting to surprises here, obviously.
Lastly, someone being the best (the smartest, the most powerful, etc.) in everything is completely unrealistic. Someone being without fail the best in something for a significant amount of time (and not just winning one competition, two competitions, or even three competitions) almost never happens, and when it does, it speaks more about luck than anything else. You can see that in sports, in chess, in LoL or StarCraft, whatever strikes your fancy. But it's even more complicated than that. Let's take being the smartest. There are countless avenues of applying your smarts, and they all take time. When you put that time in math, you fall behind on chemistry or trickery. But it's more complicated still. Math is a vast field, and you don't actually learn it in its entirety, you work only on some subjects, inevitably at the expense of others. When you don't think about something, people who do become your betters in those matters. This happens even if you are actually smarter than them and would've achieved better results were you putting your time in their subjects. But your time is limited, you are not omniscient and can do only so much. This is why Kellhus needed to be taught the basics of sorcery, for example. That subject was too advanced (not to mention dangerous) to try to discern by himself and have a chance against trained practitioners afterward.
As Bakker says, Kellhus is one intellect, two hands.
But let's take another example. Say there is a long-range shooting discipline where your results are consistently 98-100% accuracy. You are great, you win competitions fairly often. Your closest rival has only 93-95% scores. Now, imagine there is a shootout, where we for the sake of simplicity disregard luck, speed, difference in mental states, etc. Everything except accuracy. You have 98-100% chance to shoot your opponent dead. But they have 93-95% to do the same to you. This is what I'm talking about when I say some differences are negligible. Your opponent is inferior, but in a confrontation they still present 93-95% chance of death, which is game over, no more you. And this is just one opponent. That's how I see Kellhus looking at a confrontation with other Dunyain even if he considers his abilities superior.
So this whole line of thinking about someone being the smartest or the strongest looks a bit childish to me. I don't think it helps our understanding of the series, because so far Bakker consistently demonstrates admirable adherence to a realistic outlook in things he doesn't explicitly call and show as supernatural (the terms he uses for it vary, of course). Supernatural things work however he wants them to, obviously.
So, if Bakker says Kellhus is the strongest sorcerer, I understand that very generally. It wouldn't mean to me that he would invariably win every sorcerous confrontation. It wouldn't mean there aren't those who wield comparable power (though they probably would need to be Dunyain). It would mean he knows more and can do more than other sorcerers, yes. But not all knowledge is (immediately) practically useful and not all knowledge helps in battle. Not all skills and sorcerous techniques do. And even having superior knowledge doesn't mean knowing everything. For example, Kellhus wasn't able to equip the Great Ordeal with flying chariots, because he
"hasn't plumbed the secrets of Mihtrulic".
