I probably haven't seen near enough his overall work, but what I did have the good fortune to witness, he always made it look so effortless. No matter the role.
The dude had serious range... from a proto-hippie stoner professor in Animal House, to playing stiff aristocratic patriarchs in early 19th century Britain.
IDGAF if the dude was Canadian, he would have been PERFECT as Albus Dumbledore in the original Harry Potter films.