I'm all for villains staying dead, but I can make an exception with Illidan. He was such a unique character with alot of promise and Blizzard didn't do a very good job handling him in BC. Also, because of Metzen's answer and if people keep asking about it or begging for it, I think Illidan will get a redemption story.
No, Illidan was a pretty stock, typical teenage fan fic character. But he had wings and looked at a skull, so all was good.
That's your opinion, but still, he was the featured villain of BC and there really wasn't that much about him at all. I've been playing this game for over 5 years now, but I had no idea who Illidan was when we were playing that expansion and even through it I was still lost.
In Wrath I kinda knew who Arthas was at the time because I just started getting into the lore, but even if I didn't Blizz did a very good job of getting players to know who he was. Maybe a little too good. I just think Illidan deserves another shot.