Like others I'm not as sure as Karma what a "true" center is, but based on the people who play the position listed as center, here's how I'd rank Z. The five best centers in the league in my opinion are Ming, Stoudemire, Howard, Duncan, and S. O'Neal, in no particular order. There's a big drop off between that group and the next five, which includes, again in no particular order, J. O'Neal, Camby, Okafur, Z and either Gasol or Okur. There are a number of other centers not listed above that I'd trade Z for based on their lesser ages and salaries, but that's another issue.
I don't mean any of this to be a put down of Z. He's the only Cav, other than Lebron, who ranks in the top third of his competitors by position. Hughes and Gooden are probably around the midpoint of shooting guards and power forwards, respectively, and Snow would rank among the lowest of the point guards. We should all be thankful for Z's talents and good health in recent years.