With Tom Selleck playing Jesse Stone, there's been some discussion of how he'd fare playing Robert Parker's more famous creation, Spenser.
I don't think any real person is a good fit for Spenser. Even the most complex fictional character must eventually be sized up by readers/viewers. I submit that Spenser's personality is too contradictory. He is supposedly self-assured yet sensitive, good with his fists, yet witty, too.
Logically, it follows that people become sensitive to others when they begin to recognize their own flaws. It's been a while since Spenser has seen his for more than a sentence.
It also follows that a person is likely to develop a good sense of humor when he can't defend himself otherwise. ("If you can't beat 'em, make 'em laugh.") Cracking jokes while beating up someone else is more mean than funny.
It might be possible to show Spenser's varied traits in the course of a novel. Even then, I argue that his mix of traits is difficult to rein into one plausible personality. In a movie, one might successfully play some of Spenser's aspects, but no doubt some fans would say he wasn't funny enough, others would say he wasn't sensitive enough, and still others would say he wasn't tough enough.