He's known mostly as a film director, a stage director, a con man, and a magician, but Orson Welles also acted alot for other directors.
By the 1960s he was reduced to being nothing but a celebrity for hire, doing cameos to help fund his many film projects that never took off.
But, in films like The Stranger, where he plays an escaped Nazi ear criminal, Welles is really the only good thing in the film, and gives such a good performance that he makes the film succeed.
Compare that with any of his numerous guest appearances in all star 1960s films and one wonders why, despite the blacklist, other directors at least did not hire the man to act. He was reduced to scrounging for work for films made on a shoestring budget, or letting directors like Carol Reed beard for him on films like The Third Man.
Yet, even in interviews, Welles was always a consummate actor and showman:
Then, compare some of his work in his Shakespearean adaptations to that in Touch Of Evil or The Trial.
Rarely has one man acted so well in so many genres and gotten no respect. Yes, Welles has belatedly gotten his due as a director, especially for his later works. But, as an actor, while he may not have been an all time great, he was certainly a cut above what Hollywood proffers today.