I was hoping that someone with more Denon time than me would step into this thread, but since nobody has yet, perhaps I'm elected, at least for the moment.
I had a few minutes with the Denon 5000 at the San Jose meet, but didn't own the ES7 at that time (now I do). From memory, I would say the two have a similar sonic character: very open and airy sounding, very clean and clear, without boominess in the mids or bass, but with plenty of low end.
The Denon sounded excellent. My ES7 sounds quite good, but I think the D5000 is in a different league altogether. I didn't hear the D2000, but you're probably reading the same Denon threads I am, and can draw your own conclusions.
Again, I only had a few minutes on the Denons and it was almost a month ago, so I'm no authority. I think I'm on safe ground saying they have a similar sonic character and that the Denon's better, but I don't think I can honestly say more than that.
But as long as I'm comparing the ES7 to headphones I've only heard at meets, I'll say that I like it a lot more than the K81DJ, which I think is fun if you like the extra bass it brings, but which doesn't have the ES7's clarity, being a bit on the murky/boomy side for my tastes. (In other words I think I agree completely with what Asr said.)