Who played Steve Rogers in 'Captain America: The First Avenger'?

Who played Arthur Fleck in 'Joker'? Who played Bruce Wayne in 'Batman Begins'? In which film is Bruce Wayne a character? In which film is Tony Stark a character? In which film is Steve Rogers a character? Who played Loki in 'Thor'? In which film is Loki a character? Who played Natasha Romanoff in 'The Avengers'?