4. Mark Strong - Sinestro
Arguably the best part of 2011's Green Lantern, Sinestro made the entire affair watchable and Mark Strong - who played Lantern's antagonist - stole nearly every scene he was in. When the mass hysteria over the rumor of Cranston being cast as Lex Luthor hit the net, Mark String was also thought to be in the running for the "greatest criminal mind of our times". So when Cranston was speculated to have been cast, the reason given for passing over Strong was because he had already recently portrayed a DC cinematic villain ... and they may want him to again! If true, this could mean Strong returning as Sinestro in subsequent films to challenge the heroes of DC, perhaps lining up a Justice League film later on?