Well, answers to those questions do get very complicated, especially when we're dealing with on-screen (or behind-the-screen) talent; and that's mostly because it's difficult to measure something as nebulous as a professional resume against the backdrop of the entire history of entertainment. Still, I'd argue that Boen made a contribution worthy of a few words on my part, especially with my affinity for Science Fiction.
He's the only actor -- along with Arnold Schwarzenegger -- to appear in the first three films of the Terminator franchise, and that's certainly no small feat. This screen time might be more broadly considered a bit of diminishing returns, given his passing role in Rise Of The Machines (2003); and yet I'd argue his character, like Schwarzenegger's central cyborg, was given even substance to make these appearances worthwhile. Heck, even the transition of just how centrally he tied in with the whole franchise tied him up-close-and-personal to the life of Sarah Connor in the first two films.
But enough of that work ...
He certainly started out small, filling out secondary roles in film and (mostly) television, scheduled work in such franchises as TV's Wonder Woman, Buck Rogers In The 25th Century, and A Man Called Sloane before digging deep into SciFi/Fantasy with a spot as one of the recruited warriors aboard Roger Corman's Battle Beyond The Stars (1981). Though I've never read for certain, I'm guessing that it was at this impasse that his skills caught the eye of director James Cameron (who worked in the art and production department on that film), and this likely led to Cameron's casting the man as the police pyschologist Dr. Silverman, thus making screen history in whatever small way.
There was much, much more -- his IMDB.com page indicates that he amassed nearly three hundred different screen roles, some of which was voice acting in film, TV, and video games. I encourage those interested in knowing more to check out that profile right here, and I think you'll see he was an experienced Thespian, the likes of which I'm glad we have in SciFi and Fantasy.
Alas, none of us lasts forever, though talent does get a longer life with what they leave for us to explore in the days ahead. Prayers and wishes are nonetheless extended to the family, friends, and fans of Mr. Boen. May he rest in peace.