I never really understood all the complaining about "always being in Detective Mode". If you wanted to see the environment normally, you can always...say...turn Detective Mode off. Personally, I liked sneaking around with the mode on so I could plan out my assaults. Besides, if I remember correctly you usually had to turn detective mode off anyway to do the Riddler Challenges (especially the ones where you had to line up the question marks).
Arkham Asylum is a classic, though. IMO, it deserved Game of the Year nods over Uncharted 2, which was also an excellent game but it was still just an iteration on a previous installment whereas AA was a whole new game with new concepts.