Eddy Murphy sucks now...but in his heyday he was da bomb (i.e. debut self titled comedy album and "Delirious")
Surprisingly someone who I know who knows him says that despite his extroverted style he has always been mostly an introverted type.
My older sister invited a San Francisco apparently extrovert stand up comedian to a party (just looked up his number in the book and called to invite) and he showed up but in person was quiet, nice and introverted.
So its tough to tell. A disproportionate number of them seem to have emotional/mental problems as well.