It has become common and accepted knowledge that Dwight Howard is one of the biggest game-changers in the NBA today. Despite what you think about his ego or leadership, his ability to completely alter a team defensively is unparalleled right now. Finding the next Howard is a tall order, but you can bet many NBA general managers are trying to fill it.
An important thing to remember is that being a good big man is not enough. Howard has a very specific style and set of skills. There are certain players that could never be the type of big man that he is, especially defensively.
There are very specific components that such a player would have to have. Supreme athleticism and length are musts, as Howard uses those tangibles to protect the rim and anchor the defense. Rebounding is vital on both the offensive and defensive boards. Offensive ability is not a prerequisite, as Howard can score but is not all that skilled offensively.
There are many young players in the college and NBA ranks who look like they could have the raw potential to be the next incarnation of Howard. However, pinpointing which players actually have what it takes is hardly a science and is why it is so hard to run an NBA team these days.