I don't talk a lot about performance on this blog, despite the fact that I entered this field as a performer (and occasionally find my way to performing still).
However, I finally caught up with this excellent Cagney montage:
Cut up in this way, it's easy to see what was so successful about him. It wasn't just the fact that he was a tough guy -- although he definitely was -- it was that even his most serious scenes had a bit of the wildness and the exaggerated body language of the clown. His fist-fights and his slappings look like clown fights when taken out of contexts; the moments when Cagney really dances or is just crazy are really rewarding.
That's my frustration and disinterest both with many current action stars. Just because you're a big hulking male doesn't mean you have to be boring as pudding.