Like I said these guys have serious skills as players, but they are very one dimensional. And thats not really a knock on them. They do what they do at an extremely very high level. But they are not nearly as versatile as Kotzen as players, singers or songwriters. Kotzen can do pop, blues, fusion, rock, and shred at as high a level in all of them as these guys do in their one thing. Thats what makes him something truly special. He's done everything from instrumental shred records for Schrapnel at age 17, to stepping into Mr Big and playing all Paul Gilberts stuff, to rock blues and soul with his band, and also some jazz fusion with Stanley Clarke. The dude is incredibly well rounded as a player and songwriter and we havent even mentioned his voice yet. Richie has a voice similar in range and dynamics to Chris Cornell for rock, but with some soul influence as well. Oh, and did I mention that in most cases, like Prince, he plays all the instruments on his records?
Thats why hes a "virtuoso". The dude is a musician's musicians in every sense of the word.