I'm sure there will be many different names mentioned but the winner, without doubt, is Jimmy Stewart. Nobody commanded the silver screen the way Jimmy did. Feel free to argue with me.
There are others, IMHO, that are in the running however. Cary Grant. Actually I think Cary very nearly tied with Jimmy.
I'd put Morgan Freeman in this category.
Of the 3 I mentioned... now be honest.... when they are on screen are you really watching anyone else?
There are others - but I'd rather hear what you think.
Now you've noticed, no doubt, I went 'old school'. Well, bias I guess... but other than Morgan Freeman (modern day)... I only know of very few approaching the screen charisma of those I mentioned. NONE that I think their equal but some are close, I grant you. Maybe Brad Pitt? Some would maybe say Tom Hanks (great actor) but I would not.
I have a long list of modern day actors I don't think hold a candle to those I mentioned. Some of them 'mega famous'. BUT... I won't list them here because you may have one of them at the top of your list... which makes sense since this is subjective....... or is it?
They call it the "It Factor". Who, in your opinion, had "It". - JamesJM