Like many sabermetricians, I have an unhealthy affection for the knuckleball and the pitchers that throw them.
Maybe it's because of the way the ball dances toward the plate, or maybe it's because they don't throw much harder than your average Little Leaguer.
Whatever the reason, I think it's fair to say there just haven't been enough knuckleballers in the big leagues.
Here's a look at how the most prominent knuckleballers of the Retrosheet era compare. We're only looking at years when the pitcher actually threw a knuckleball (so Joe Niekro is 1971 and beyond, for example). Data is from Sean's Pitching WAR database and the knuckleball identification is from Rob Neyer by way of http://www.oddball-mall.com/knuckleball/list.htm.
Phil Niekro is head and shoulders above the rest of the pack. I'm surprised that Wilhelm doesn't fare better - although I shouldn't be. He spent so much time in relief that it's almost unfair to compare him to the group.
I didn't remember Tom Candiotti as being that good but he put up six All-Star caliber seasons. And Wakefield keeps plugging along, but he's only clearly better than Joe Niekro on this list.