When cata came out, everyone was "booo: we got these badass dudes in Illidan, then Arthas, then a dragon?? bhooo"
This thing went on a bit, and while i would never say that Deathwing as a character has more charisma then these other 2, i would say he is just behind.
First of all he has many accomplishments that simply other villains didn't match.
The fact that he literally changed the landscape of the world was incredible, and while you may or may not like the world post-cataclysm to me it was at least already an impressive mark left from the villain to the players.
Second, he was acutally THERE WITH US.
Unlike most other villains that appears sporadically during the expansion and you mostly see them only in their raid, with deathwing it was different:
He was literally free roaming all over Azeroth.
I still remember that i was shitting in my pants when i was in the fking Barrens and everything turned red, the sky, the grass all red. Then you start see Flames around you: You turn up your camera to the sky and you see big ass Dragon flying over the zone - killing you in the process (but earning a nice achivement that sadly Blizz gave for free later).
This is all to say that we need to see more VIllains like him. Leaving a real impact on the world, the players, the characters.
Deathwing you were my hero.