I think of Spock as being a prodigy of sorts, perhaps a Da Vinci of Vulcan?
Asides from being a computer and science genius, Spock is highly skilled in several other areas including engineering, communications and tactical. He's what you might call a polymath and his knowledge has been a factor in providing solutions to situations that would likely have had a different outcome had he not been present.
These polymath traits were reused from Data in TNG. The only difference is that while Spock abstains from emotion, Data is completely incapable of them. We know from many episodes of TOS that Spock understands emotion just as well as humans do, but he doesn't admit this because it's not the "vulcan way". His understanding of emotion is arguably his biggest advantage in his role as first officer.
Of the other vulcans we have seen, Tuvok, Saavik, Taurik and Vorik don't really have anything on Spock. Fair enough, Saavik was only a cadet or a junior officer in her appearances, whilst Tuvok's knowledge lies in the arts of investigation and self-defense - appropriate for his career. Taurik and Vorik are both junior engineering officers and didn't make much of an outstanding impression in any of their appearances. We could argue that Valeris is a particulary gifted vulcan as she was the first to graduate top of the class at the Academy. Then again, she seems to be on the command path and wouldn't have the scientific or engineering expertise of somebody like Spock.
Sarek is a difficult one, we know he attended the Vulcan Science Academy, beat Spock in music contests, gave Spock his first lessons with computer and is one of the top diplomats in the history of the Federation, but it's very possible that Spock has surpassed Sarek in many shared fields of expertise. For example, whilst Sarek was stuck on Earth at Starfleet HQ during TVH, he was at a loss to suggest anything other than sending a distress call during the probe crisis. Whereas Spock realised that the probe was transmitting whalesong and came up with a solution to the problem in a short space of time.
It's a difficult one, the likes of Surak might have surpassed Spock intellectually - Surak managed to bring order to a warring planet and created a system of self-discipline that eventually became the standard vulcan way of life. Then again, Spock managed to reach out to the Romulans and get many of them interested in a re-unification of their species, something which had previously been considered unlikely. You also have to look at Sybok as well, Spock openly said that he was considered a prodigy and it was expected that he would one day be known as one of the great philosophers of Vulcan. We know that Sybok had some powerful telepathic abilities and despite being openly emotional, he still retained a great deal of control over the more "passionate" vulcan emotions. Then again, by the 24th century it's clearly shown that Spock has finally embraced his human side and found a balance between emotion and logic.
