Tom Selleck is just such a likable guy. He's believable whether he's running around in a swimsuit making David Hasselhoff want to grow up to be him or taking on the bad guys.
But Magnum's biggest cultural contribution may very well have been its willingness to openly examine some of the troubling long-term issues that Vietnam veterans faced as they transitioned back into civilian life after the war.
When every other adolescent male of the '80s and I grew up, we wanted the life of Tom Magnum... and periodically solving mysteries using a combination of smarts, toughness and mostly chutzpah.