Ok, mine isn't as creative as others, and is a bit if a cheat, so I don't expect many votes.
Green Lantern
Written and Directed by Joss Whedon
From the man who brought us Serenity and The Avengers, comes the origin tale of Green Lantern Hal Jordan.
Brief synopsis: Green Lantern Abin Sur crash lands on Earth while transporting a prisoner. Pilot Hal Jordan finds him and the ring, you know the story. While training with his new GL Corps mentor/partner Sinestro, he learns that Abin Sur's prisoner Atrocitus has returned with his followers to wage war on Abin Sur's replacement/Earth. You get the idea.
Hal Jordan/Green Lantern: Paul Newman (1960s); handsome, confident, charismatic, damn good leading man
Sinestro: Gary Oldman (1990s)
Carol Ferris: Amy Adams (present day); beautiful, easily one of the best actresses working today, can go full Star Sapphire in sequels
Ganthet: Ian Holm (any time period works, really, considering he is playing a make-up covered alien who is really old anyway)
Atrocitus: Keith David (any time, really, because he will be voice/motion capture)
Abin Sur: Doug Jones (preset day)
John Stewart (cameo): Denzel Washington (1990s)
Guy Gardner (cameo): Bruce Campbell (1990s); both of these characters could come back for sequels
Martin Jordan (opening sequence, flashbacks): Dennis Quaid (1990s)