With Lawrence Montaigne, Gordon Jackson, and David MacCallum in The Great Escape, John Sturges, 1963.
Garner's screen work gently rebuffs hard analysis. It isn't that what he did lacked complexity or sophistication. But he had a way of relaxing into whatever character he was playing that only made you want to be by the character's side, rather than "understand" the character. Strain, either visible or subtextual, was not part of his performing vocabulary. This could have the almost paradoxical effect of bringing an unusual depth to less-than-fully-conceived persons. While Charlie Madison in 1964's The Americanization of Emily has righteousness on his side, scripter Paddy Chayefsky's writing, eloquent as it is, has an unrelenting stridency that, coming out of pretty much any other actor's mouth, would have made him a scolding drag. Garner's voice, the set of his jaw and brow, his gait, make you warm to the character even at his most uptight. Similarly, part of what makes The Great Escape such a great sit is the fact that you'd follow Garner's Hendley anywhere, any time.
He clearly had an innate sense of his limitations. No, he was not Stanley Kowalski, nor was meant to be, and he did not waste his or his audience's time pursuing such feats. Which didn't mean he couldn't swing a little; to watch him run a near-full gamut of sexual confusion in Blake Edwards' 1982 Victor/Victoria is to witness as acute (but compassionate) a critique of machismo as Hollywood could muster at the time. By the same token, his work in later pictures such as Murphy's Romance provided little object lessons that "masculine" and "gentle" need not be mutually exclusive terms.
He worked an awful lot, and whatever he was in, good or bad, you were always glad to see him in it. If that doesn't constitute a laudable performing career, I don't know what does.