Van Johnson was a favorite of my mother's. I liked him, too, but better in his military roles. I remember, several years ago, watching "Too Many Girls", the movie that introduced Lucille and Desi one to the other, and thinking that one of the dancers looked like a real young Van Johnson...and it turns out it was he performing in his first film.
I thought that his later guest turns on TV were a bit bombastic, but that was perhaps the direction he was given.
BTW, he turned down the role of The Untouchables', Elliot Ness, which made Robert Stack a huge star.