Let's define the Joker in this...

Rating: 7/10 (17 August 2008)

I'll start out by saying that I am a fan of the Batman franchise and enjoy both the graphic novels and a number of the films (Schumacher..dear me!), so I do consider myself objective overall of this franchise.
I gotta just say that Nolan has done a great job on both his efforts and captured the "dark" part of the knight, with great scripts, Bale and supporting cast are superb and very true to the original intentions of the novels and ideals that Kane / Finger and many, many others have moulded the legend into over time.
But - where this joker is concerned regarding Ledgers portrayal; then I feel that it is fantastically overrated. If you take the novels where Joker is the main protagonist, he has more to him than smack his lips or wipe his greasy hair back! Ledgers take on the psychotic prince of clowns is a 1 dimensional affair at best. Burton / Nicholson's depiction was closer to the overall character - the swinging pendulum between manicness and sadness (bi-polar) wrapped around the need to kill, the deep affection and true deadly respect for the Batman - sure, all touched on by Ledger but these are the core traits of the Joker, where was the outlandishness and over the top deadly playfulness?
Ledger, IMHO, never had the artistic talent, depth or direction to be mean enough and psychotically twisted to do the Joker justice. He only really nodded to this murdering liars twisted past & or formative years (family etc...)superficially . The script and direction saved him overall but casting a stronger character initially was the key, never can the script or direction cover all the bases in this uniquely difficult role to cast.
Overall - as callous as it may sound but the only 'positive' thing is that they will have to search for someone else for the franchise to continue. I say give Jim Carrey a crack at it...