He was a good character, unfortunately DS didn't adequately explore him. Also he's a bit MUHUHAHAHA in his appearances in Twilight Highlands.
I mean, WoW is not really good at character exploration in general, it's not that kind of game. I do wish he had a better sendoff though. Same goes for Kael'thas and Illidan (sorry TBC hipsters, but the main stories in that expansion were actually incredibly disappointing).
In fact that tears it, I'm going to vote Kael'thas as the worst main villain in the series because he shouldn't even have been a villain in the first place!
P.S. If you want to get all nerdy and talk about relative power levels, Deathwing could've blown Arthas into a million pieces with one well-placed fart. But Arthas was a huge character in everyone's mind because we spent two (!) campaigns playing as him in Warcraft III.
---------- Post added 2013-05-17 at 04:26 AM ----------