1) Brandon Routh
Arrowverse Role: Arrow/The Flash/Legends of Tomorrow/Vixen as Ray Palmer/The Atom
Other DC Universe Roles: Superman Returns as Clark Kent/Superman, The Batman as Everywhere Man
Most of the actors on this list – with the exception of semi-regular character John Wesley Shipp – are just guest stars. Brandon Routh, however, is a main character of the Arrow universe, as he’s turned up as Ray Palmer/The Atom across the three central shows.
Of course, as any Superman fan knows, he’d previously played the Man of Steel himself on the big screen in 2006’s Superman Returns. That same year, he also lent his voice to the villain of an episode of The Batman.