First, I'm going to go through my choices for the DC Cinematic Universe, where these actors will be included in the Justice League films and their own subsequent film(s). Secondly, I'll add my choice for Green Lantern (Hal Jordan) only for a small recurring role in CW's existing DC Universe. Note that I'm going to focus mostly on the human characters in this one.
DC Cinematic Universe
1.HAL JORDAN - James Marsden
Marsden is experienced, talented, handsome, a good actor, and can lead a film. He is also a well known actor. Now that the X-Men franchise is moving on from the past cast, it may be the opportunity for Warner Bros to eye the ex-Cyclops actor for a role that needs a good revamping. At the age of 41, he's an ideal Hal Jordan alongside Ben Affleck.
2. CAROL FERRIS - Michelle Monaghan
Monaghan has been a past fan favourite for the role of Lois Lane, but having seen her alongside James Marsden in "The Best of Me", I'm left convinced she is the ideal actress for the role of Carrol Ferris. She has appeared alongside leading men such as Tom Cruise, Morgan Freeman, Robert Downey Jr, and more, and has been able to command her presence on screen and play the "tourchured" and "unpleased with her lover" love interst/wife. She has also been part of many action films such as Source Code, Gone Baby Gone, and Eagle Eye. It's time for the actress to step up and into her defining role for the World Audience.
3. THOMAS KALMAKU - Manish Dayal
The young Indian-American actor was wonderful in his "leading" role in the Hundred Foot Journey alongside legendary actress Helen Mirren. He will appeal to a larger market (South Asia?) and bring in a younger audience who have seen him in recurring roles on ABC's Switched At Birth, and CW's 90210. He will also be great for some diversity in the films.
4. JIM JORDAN - Matthew Bomer
Half of the comic book world was convinced this man would be their next Superman, and he almost was! But now that we have the perfect Superman in Henry Cavill, we can move on and explore putting him a role that requires some "questionable" actions. Jim Jordan is the younger brother of Hal, and becomes very curious about what his brother is up to when Journalist Sue Williams suggests that Hal Jordan may be Green Lantern. The Golden Globe winning actor can turn Jim Jordan into a fantastic frenemy (Enemily?) in the new franchise, and cause a lot of trouble in Hal's life.
5. SUE WILLIAMS - Elizabeth Banks
Elizabeth Banks has played a lot of questionable roles in the past and is almost ideal to be a inquisitive reporter for a modern day Tabloid that hopes to expose Green Lantern and the rest of the Justice League for who they really are. Banks has recently been in The Hunger Games franchise and is a known face to audiences, and people would love to see this blonde beauty fight it out with Lois Lane on the News.
6. SINESTRO - Christoph Waltz
The Academy Award winning actor needs no justification really. His accent and experience in playing epic villains with a moral/immoral conscience makes him an ideal Sinestro in the big budget films. He would be an actor welcomed to the role by fans and critics alike. Although he doesn't have past experience in CGI, but neither did many other actors before joining a Comic Book Movie.
CW's DC Universe
HAL JORDAN - Scott Eastwood
The up and coming actor is the son of legendary actor and director Clint Eastwood. Scott has recently appeared in Fury, although his role was very small, he held his own and stood out amongst the full-fledeged cast. Scott has an aura of cocky confidence and the build of a soldier, which makes him a great casting for the CW's interests. He is not attached to any long-time commitments and surely would be attracted in a recurring role as Hal Jordan in ARROW and THE FLASH.