Greta Garbo.
John Wayne was the first person to come to my mind too.
I really didn’t (and don’t) want this to turn into a debate thread but could you just very briefly justify that? I know she was great and I learned about her in college and all, but she had a relatively brief career - half of which was in the silent era - was in nothing that is still popular today, and I doubt very many people under 40 have ever heard her name, much less could pick her out of a lineup of 3. I’m really curious what makes you think of her when someone says “Biggest Movie Star of All Time” (note not “greatest movie star” or “best actor”.)
The first thing that came to mind was Cary Grant, and I don’t even think I’ve seen a single movie of his.
That guy Castov Characters was in freakin’ everything.
Biggest woman movie star: Elizabeth Taylor.
Man: Cary Grant. Class from the ground up, and a draw to audiences no matter what the movie was.
You really should. He’s got a number of great films out there that really reward viewing. Many of which are a bit more modern than you might expect.
I’d suggest checking out People Will Talk for an excellent look at his presence on the screen. It’s not a comedy in the manner of many of his more famous films (Those are well worth viewing, too. Cary Grant started with pratfalls, and made great use of his skills with them.) but it shows how he could with tone, and expression alone, communicate with the audience, inviting the viewer to share his unvoiced thoughts.
Oh, definitely Cary Grant. The first thing I thought of when I saw the thread title was the joke from the Mel Brooks/Carl Reiner sketch “The Two-Hour Old Baby” --“Hey, everybody knows Cary Grant!”
Also, I fuckin’ hate John Wayne.
Henry Fonda.
Katherine Hepburn.
Or maybe Pauly Shore.
North by Northwest is good, and seems to have influenced a ton of movies.
To me, there are two movie stars who stand head and shoulders over all the others. They’re both icons, they’re both so famous that practically ANYBODY in the world can do a bad imitation of them, and practically ANYBODY in the world would recognize a bad imitation of them.
John Wayne and Humphrey Bogart.
Well if that’s the criterion, I’d have to say Bette Davis.
That’s an interesting observation and quite true. In fact you can just about get away with any sentence ending in “Pilgrim” or “sweetheart” as the case may be.
Sir Laurence Olivier.
This thread is now closed, no more names needed.
Yeah, anyone who says anyone but Chaplin needs to offer a pretty strong argument for their case.
People who have never seen a Chaplin film can immediately identify him from a still photo- or can give an accurate physical description from memory if no photograph is provided. People who have never seen a single one of his films, in addition to being able to visually identify him, can also give a description of his act.
This familiarity is international.
This familiarity continues over 70 years past the peak of his career.
Anyone who says anyone but Chaplin needs to offer a pretty strong argument for their case.
Anyone who says, “Anyone who says anyone but Chaplin needs to offer a pretty strong argument for their case,” twice must have a pretty strong argument for their case! 
If I may broaden “biggest movie star of all time” to include not only fame as an actor/actress, but also total film industry influence and global recognition, I’ll have to cast my vote for America’s Sweetheart, Mary Pickford. Her name as an actress has largely faded from the public consciousness only because her flame flickered out so many years ago and her films, being silent, are no longer popular. In her heyday however, she was an international megastar of the highest order. She was much more than just a talented and popular actress. With keen intelligence and tenacity, she made a formidable businesswoman who used her considerable clout in Hollywood to help make the film industry into what it is today. As a true pioneer, Pickford’s resume includes many film industry firsts (see links below). Her famous mansion, Pickfair, which she occupied with husband, the “King of Hollywood”, Douglas Fairbanks, was an American Camelot, hosting the era’s most legendary figures as regular guests. Indeed, the greatest “complete package” movie star of all time has got to be “the girl with the curls”.
And anyone who says, “Anyone who says, ‘Anyone who says anyone but Chaplin needs to offer a pretty strong argument for their case,’ twice must have a pretty strong argument for their case!” even once, must have a pretty strong argument for their case!
Godzilla
Huh? Why? I don’t think of him as a movie star at all, much less the Biggest Movie Star of All Time. I think of him as an extremely well-respected stage actor who did some film. Off the top of my head I can’t think of any blockbusters he starred in, much less played the lead in.