I think the distinction people are making between an enemy and a threat is a ridiculous notion.
http://en.wikipedia.org/wiki/Enemy
An enemy or foe is an entity that is seen as forcefully adverse or threatening. The term is usually used within the greater context of war, to denote an opposing group as a threat.
http://dictionary.reference.com/browse/enemy
1. a person who feels hatred for, fosters harmful designs against, or engages in antagonistic activities against another; an adversary or opponent.
2. an armed foe; an opposing military force: The army attacked the enemy at dawn.
3. a hostile nation or state.
http://www.merriam-webster.com/dictionary/enemy
1 : one that is antagonistic to another; especially : one seeking to injure, overthrow, or confound an opponent
2 : something harmful or deadly <alcohol was his greatest enemy>
3 a : a military adversary
b : a hostile unit or force
Hell, for good measure
Black's Law Dictionary:
1. One who opposes or inflicts injury on another; an antagonist.
2. An opposing military force.
3. A state with which another state is a war. -- Also termed public enemy
4. A person possessing the nationality of the state with which one is at war. -- also termed enemy subject.
5. A foreign state that is openly hostile to another whose position is being considered.
To try to say one is less of an enemy just because they did less actual damage but were conceivably a bigger threat is just ridiculous.
I'm sure people were probably much more threatened by the Nazi regime and during the Cold War than people are from AQ. The idea of enemy often has a strong connotation of being an opposing military force. I wouldn't call AQ an opposing military force. Military force conjures up in the mind of going head to head (not 18th century line up and shoot) but at least fighting in a more open manner than hijacking planes and hiding in the desert.
The people on the idea that "Osama was more of an enemy" are silly playing a semantics game that ultimately doesn't mean much. Osama and AQ will go down in history, but they will not be nearly as talked about as Hitler in WW2 or the Cold War with the USSR.