I've been contemplating this question ever since I finished up Batman Arkham City. Strange is a brilliant chessmaster yet Hurt totally broke down Bruce mentally, physically and put his cunning to the ultimate test. Although if you consider the challenge in the final stages of Arkham City you could say the same of Strange.

So who is it?

Dr. Hurt

or

Doctor Hugo Strange

Dr. Hurt is a better enemy of Bruce Wayne 
 
Dr. Strange is a better enemy of Batman

@The Stegman said:

Dr. Hurt is a better enemy of Bruce Wayne Dr. Strange is a better enemy of Batman

Brilliant summary of feud between Bats/Bruce's enemies. Although if Hurt is such a Wayne clan enemy the dude should've met Bruce outside his alter-ego rather than when he was in it. Would've made things interesting.

Tough call,Hurt is a criminal mastermind.Hugo is a mad scientist,overall Hurt had the fortune of being the main villain in a storyline which affected the Batman status quo massively while Hugo has'nt really been in any major story aside from Monster men.But Hugo has the potential to be used as a recurring villain,Hurt is a one time deal.