Personally I don't see Alexander's unusual character traits as flaws. It certainly doesn't make him a worse general that he didn't particularly care about how Macedon survived after his death. I'd say the kind of deserved arrogance and narcissism he possessed actually makes him a more compelling historical figure, which was probably his intent as well. He knew full well the kind of mark his actions would leave on history, and his ego merely embellishes that. When a person like Alexander is so clearly superior to any contemporary figures, I think it only appropriate that he not hide behind false modesty. His persona, in fact, is probably the reason he's being considered right now as the top commander in history. Not only did it contribute to his victories in the effect it had on the morale of his troops and that of his enemies', but it simply draws people to him, even posthumously. I still don't necessarily think he was the best battlefield general the world has seen, but I think he was perhaps the greatest master of how history works, in terms of establishing himself as an icon of greatness.