It was a huge security failure but I can't agree that you can somehow pin this on the President. It's pretty hard to imagine that Bush was told about an imminent attack and said "naw, don't worry about it".
It was a failure between our so-called Intelligence agencies. Most of the upper ranks are political appointees, not true intelligence operatives. They jealously guard their little empires and worry about getting credit.
Personally, I thought Bush was as dumb as a box of rocks and I hated the sight of his smirking face. However, I can't possibly think he was directly to blame for the events that occurred. For using those events to create a war in Iraq for the primary purpose of looting the country by his friends, yeah, I do blame him for that.