I'll humor the Smallville universe and state the cast that has been seen and or shown, or has yet to be seen such as the JSA i will not touch and leave the actors in their various roles.
George Stults - Hal Jordan (The Green Lantern)
Scott Porter - Barry Allen (The Flash)
Megan Gale - Wonder Woman
Paul Wesley - Batman
Ryan Kwanten - Ronald Raymond (Firestorm)
Zach Gilford - Ray Palmer (The Atom)
Chris Carmack - Despero
Kevin Durand - Lobo
Mehcad Brooks - Steel