Well he's had some rolls with different looks, certainly long hair as Conan, even Stallone did like half a dozen movies looking the same but for costumes. Your appearance is huge when your performance doesn't do much to allow folks to see you as a unique character. Tom Hanks looks the same in a lot of movies, but his performance almost always make you read into each role as a new person. Christian Bale's another good one nowadays, his Bruce Wayne and his role in The Prestige don't look too different, but he plays each character uniquely and you believe him as what he's playing.
Arnie and Sly are very entertaining, but a lot of times you can't see them as just themselves again in a different story. Lucky for Sly, his bread and butter roles are so different as far as character, between that and looks you never see them as the same guy, I don't anyway.