With the rule changes in the mid-2000s coupled with the change in defensive philosophies whereby many defenses crowd the ball side and come off their man to help much, much earlier than in the past, and on offense the general change leaguewide towards spread offenses to counteract those defenses (necessitating more outside shooting, slashers who can attack the paint and take advantage of the handcheck rules and the open key)- these changes have gradually phased out the traditional big man and moved the league more towards PFs who can shoot and on defense can defend the pick and roll and rotate for help more quickly.
That's my long explanation for my main point that traditional big men are not as important in the NBA anymore, the changes in the league have led to a faster game than before, driving the # of teams that run their offenses through a true post presence down. A lot of the Centers on the list above are essentially specialists, asked only to be great defenders, to rebound and to maybe run some pick and rolls (Asik, Sanders, Chandler, Jordan, Varejao, McGee) Some teams don't even start a true Center anymore such as the Heat or the Celtics. So the Center position tends to be considered the weakest position as for elite talent in the league. It has a lot of very good players but no one in the top 10 in the NBA. Gasol might have had the best year out of the bunch, he really has been great defensively and offensively he has done a little bit of everything for the Grizzlies. Personally, I have him, Howard and Duncan (he's more of a Center than some of the guys on the list) as the top 3 Centers for this year.
