I'll preface this post by saying that almost all of the centers in the all-time greats discussion retired before I was born, so I am going to comment on the people that I've actually seen play, not those that I've only seen a few highlight reels of.
You can't compare people across generations based on stats, or even their skills (yes! I just said that!) Why do the stats, skills, et al. not translate across the decades? If Dwight doesn't play the style that Hakeem did and averages 17 ppg and 13 rpg to Hakeem's 22 and 11, how can you compare the two based on skills? Yes, Hakeem had a very complete game, but if Dwight can put up similar numbers without all the fancy footwork and shooting, how can you hold that against him? Perhaps Dwight never developed those skills because he could still excel with the approach he uses? And for stats, well the game has simply changed so much that you can't compare the stats and say that this number means this and that number means that. If Hakeem played when Wilt did could he have put up point totals nearing 100 on a regular basis? Maybe. That's it - maybe. We really don't know how he would have handled the style of basketball played in the 60's, so we can't compare him to players of that era. The way I see it, the best centers need to be head and shoulders above the competition they played against. So, let's look at Dwight against his competition. There is a general consensus that he is the best center in the league at the moment, but is he that much ahead of the pack? Well, he was fourth among centers in ppg, and first in rebounds in blocks this season. He recorded over 100 more rebounds than the next best center, and over 50 more blocks. Pretty dominant, stat-wise at least. But let's talk about his actual play. The Celtics have shown that even when he is the primary scoring option for his team, with the Celtics holding tight on the 3-point line and Perk left to defend Howard one-on-one, he cannot control and dominate a game like some of the others mentioned in the argument. In the Eastern Conference, against a slew of other good, young centers (Perkins, Bogut, Lopez, Lee) has Dwight been so much better than anyone else has been? I don't think so. So, in my opinion, he is not an all-timer.