It’s impossible to name the best DM out of the DMs I’ve had. They all were very different, and they all had good moments.
My cousin Rutger was my first DM. Actually, we always ran our campaigns together. We would take turns DMing and playing. Sometimes we would prepare our own separate adventures, but more often we would prepare for the game together, and decide who would DM two minutes before we began.
My friend Alex was my DM for most of my time at art academy. Alex was a big horror fan, and read a lot of Stephen King. He was attracted to Ravenloft, and ran adventures in that setting exclusively .
Being both an art student and a horror fan, it’s no surprise Alex was very good at building atmosphere. His Ravenloft game often went beyond the gothic horror the setting usually provides, and our PCs encountered scary dreams, serial killers, and a rusty petrol station from another time. He often used out-of-game elements like music and lightning in his game
My friend Martijn was a believer in The One Way: the DM providing the railroad and the player’s staying in character as much as possible. His favorite setting was Al-Qadim, and for the most part he ran published adventures. I have written about those before (here and here), because I’ve used them for my own Al-Qadim campaign as well, and sometimes I could see he had difficulty making the adventures work. That’s not to say he was a bad DM, it was the adventure’s fault. He was especially good at using props: clay amulets, handwritten documents, that sort of thing.
Martijn was running his Al-Qadim campaign when 3rd Edition came out, and converted the campaign to the new rules. In hindsight, the shift from a more story-oriented game to a more combat-oriented game was very clear. The story elements were still there in 3rd, of course, but because the characters had more combat-oriented abilities and the fights took a bit longer, there was definitely more combat in the game than before.
My brother Jorrit DMed Dark Sun for a bit, decided he didn’t want to play AD&D anymore, played and ran a lot of games in the Storyteller system, and came back with 3rd Edition. When 4E came out we started a campaign together, each of us running adventures in turn, but he quickly decided 4E wasn’t for him and left our group. Now he mostly plays Pathfinder.
I’ve played in two of Jorrit’s campaign: the Banewarrens campaign and his Castle Greyhawk campaign. Both had the same faults, pretending to be large megadungeons but really being 3.5 adventure paths. However, both have enough fun set-pieces, and Jorrit is especially good at those. He was also good at managing a big rule-set like 3.5 and Pathfinder.
So all of the DMs I’ve had were the best in some aspects. It’s interesting to note all of them were especially good at things I don’t do in my games. I don’t use music, and my games are more about ideas than about atmosphere. I hardly use any props, and while I’ve had long miniature combats in my 4E game, of course, I’m not really that good at the tactical side of the game. Maybe it’s because I’m not very good at those things that I admire their skill with them.