I hate stuff like this though
Why has it become cool to hate on Depp?
Just casue Pirates 3 and Sweeny Todd sucked?
Depp is easily one of the 5 best leading men in hollywood still, he's made some duds recently but he still is really really good and a completely original actor.
Don't forget, Christian Bale was in crap like equilibrium and reign of fire before Batman, and Ledger was mulling around in crap to passably good stuff like The Order, Four Feathers, The Patriot, and A Knights Tale too.
Depp has a greater history of being a phenominal actor, than his recent 2007 struggles show-he would be a fantastic riddler
again though, my preference between the two is Pearce but by no means do i think Depp would make a bad Riddler