If the NBA is a shooting guard famine, the center position is extinct by starvation. Howard is the only unquestionably elite center in the league. It isn't even close.
This isn't to say that Howard is anything less than a great player. He dominates the game defensively and has a superb offensive game. While NBA analysts dream about him scoring 30 points per game (because, you know, there isn't another great center in the NBA), Howard is still a force to be reckoned with.
Howard is to defense what LeBron is to offense: a player who can change the game by his mere presence. He grabs rebounds and records blocks with ease, but his true value is sitting in the paint. When Howard is down low, opposing offenses take notice and change their strategy. There aren't many players in the history of the NBA who can say the change the game by just playing.
Second Team: Tyson Chandler
Chandler won't put up eye-popping stats in New York; however, he will make the Knicks a substantially better team. Like Howard, he effects the game by his presence, albeit to a lesser extent. He proved in the Finals to be a LeBron stopper. He manners the center position with respect to opposing players. I don't think the Knicks are a better team than Heat, but I do think if they met in the playoffs, it would be a close series.
Third Team: Al Horford
Horford may not be the offensive player that Brook Lopez and Andrea Bargnani are. However, considering Lopez and Bargnani each averaged less six or less rebounds per game last season, I'll take Horford (9.3 rpg, it turns out that rebounding is an important part of the center position).