Yes, he is. Quite a feat considering the monsters in NW. You're just being presumptious thinking the wg considers him an enemy, that spot is mainly reserved for luffy and lufffy only. Never has oda named anyone the wg enemy, cause no one is of equal standing with it, not an organisation (revos) and certainly not a person (dragon)
Do you understand what an "enemy" is??
Enemy: - a person who is actively opposed or hostile to someone or something.
- a thing that harms or weakens something else.
Considering Dragon has done more damage to the WG than the "Monsters in NW".. and hes considered a threat by those who met the reverie.. he is very much an enemy of the world government. And that spot is not "mainly reserved for luffy"... Luffy will be taking it over after his father.
His father is the man who is constantly weakening the WG, and taking away countries from under the WG's control.. Yet despite the WG barely having any information on him.. they marked him as the World's most dangerous man.
The final war from the looks of it will be : The revolutionaries vs The WG, the strawhats will most likely join the Revolutionaries for the fight.
If you think a single crew is taking out the WG, then you're very much overrating the power of a "main character".. especially when Oda isn't a stupid writer who'd pull a Naruto like ending.