Socrates is generally presented in Plato's dialogues as being better at some skills than self-styled experts. He is presented as being superior at rhetoric, for example, and at debate for the sake of debate. There is also indication that these are pseudo-skills, not involving genuine knowledge of anything. Thus, I take it that the implication is that one who knows that he has no knowledge has exactly the right kind of knowledge for these pseudo-skills, and that's why Socrates is even better at these skills than people like Gorgias and Lysias who think it's possible to have real knowledge of such things (and that they themselves possess such knowledge). Perhaps the knowledge of etymology Socrates rather oddly displays in Cratylus is an example of the same phenomenon, if we interpret that dialogue as ultimately favoring the conventionalist view of names (as I have some tendency to think, though I admit I haven't thought about that dialogue a tremendous amount).
I can only think of one case of a dialogue where characters are presented as being completely uncontroversially masters of a completely uncontroversial skill, and where their possession of this skill gets any particular emphasis. The case is Theatetus, where both Theatetus and Theodorus are presented as having great knowledge of mathematics. Theatetus is, of course, even credited with a considerable mathematical discovery when we're first introduced to him. There is no effort to suggest that Socrates could match, much less exceed, the mathematical skill or knowledge of Theatetus or Theodorus; Socrates is shown as having some understanding of mathematics in Meno, but nowhere, in Theatetus, Meno, or anywhere else, is he presented as being on the level of Theatetus, making original mathematical discoveries. This seems to fit well with the previous point; when a skill is real, when it involves real knowledge, long study and effort are required. You can't fake real skills just by knowing your limitations.
So far, I think I haven't said anything particularly uncontroversial. However, there are more interesting cases. It seems to me that Socrates is consistently shown as being more skilled at interpreting poetry (that is, religious tradition) than anyone he talks to. I do think that this fits the pattern of skills like rhetoric; that although he's usually somewhat cautious how he states it, Plato does advocate a fairly thorough skepticism about religious tradition. Of course, in the Laws Plato advocates harsh punishment for atheists, which is a problem for my thesis here. Apart from my usual dodge of saying I think he was getting senile when he wrote that, I would point out that given his explanation of why atheists are bad, it is not unreasonable to interpret him as defining atheism as the rejection of the existence of forms (and indeed of any kind of truth), rather than as involving doubt concerning traditional gods.
Philosophy is another vexed case, especially given the difficulty in separating it from sophistry. I admit to having a tendency to think that for Plato sophistry is for the most part incompetent philosophy, and not some entirely separate thing, despite what's said in Sophist. I particularly recall hearing M. M. McCabe explain fairly convincingly that Euthydemus and Dionysodorus were metaphysical theorists, who produced bad arguments because their metaphysical theories were bad, not because they weren't trying to produce good arguments. If she's right, if that's true of even those two, then I think nearly anyone Plato presents as a self-styled philosopher, sophist, or teacher of virtue is probably to some extent a philosopher. There may be hope even for Gorgias.
So, how does the philosophical skill of Socrates rank? And what does that tell us? I'm unsure of the first, and even more so of the second. But let's look at examples. He certainly is vastly superior in this respect to the brothers Euthydemus and Dionysodorus. He also appears to be the superior of Thrasymachus, though Thrasymachus certainly shows signs of being able to do philosophy (even if he doesn't seem to emphasize the value of doing so); the idea of distinguishing between strict and loose senses of skill or expertise comes entirely from Thrasymachus, without even the tiniest bit of help from Socrates, and he explains the distinction very clearly, though Socrates ends up being able to make more effective use of the distinction once it is in play. Clitophon also seems to suggest that we are supposed to think of Thrasymachus as some kind of philosopher, though I would not go so far as some of the Straussians who think Thrasymachus in Republic is closer to the views of Plato than Socrates is.
Protagoras also makes some quite impressive arguments in the dialogue named for him, though overall he has trouble keeping up with Socrates. Still, I have to say that my impression is that Protagoras looks worse when you evaluate him on the quality of his rhetoric than when you evaluate him on the quality of his arguments, which if I'm right would have quite interesting implications. Socrates' summary of their argument at the end puts them even, though of course his sincerity in comments like that is especially suspect.
Simmias and Cebes concede defeat in the end, but they both present quite interesting arguments. One also can't help but wonder whether they might be pulling their punches; how hard would a sympathetic person really try when arguing that there may be no afterlife to someone who is about to die? So, again, hard to compare, but at least I think Socrates is not presented as the overwhelmingly superior philosopher.
Finally, old Parmenides is able to completely crush young Socrates. Perhaps this is not a fair fight; perhaps the message is that long practice is extremely important in this area. But surely Socrates outright losing has some great significance. I'm just not sure what the significance is. Maybe we are supposed to take the message of Clitophon seriously, maybe Plato really did think Socrates fell short in not trying harder to develop some positive theory? Not completely crazy, especially as Plato seems to have done more in that direction than Socrates did. Or maybe there's some other significance I'm not getting.
Anyway, I really should stop this practice of not posting for a month and then feeling I have to write a book to try to make up for my slacking.