Yea, the Joker is one of the most complex and interesting characters in the entire DC universe. The duality he forms with Batman is incredibly ironic and creates and strange relationship between the two, one which was masterfully portrayed in the recent film (The Dark Knight).
I definitely prefer the more maniacal, sadistic version of the Joker. Mainly because I feel that it suits the true meaning of the character much more appropriately and more effectively solidifies himself as Batman's polar opposite.
Without the Joker the Batman franchise wouldn't be half of what it is today. He is truely a staple within the Batman franchise and the entire DC universe as well.
And yea....the Joker meets the Mask was a bit too much.
Joker is like a twisted Batman. He is smart and uses a lot of gadgets to get his work done. Joker has no pity for anyone even the people that works for him are like expendible that makes him the most evil villan around.