2. Ron Perlman
Along with the likes of Ryan Reynolds (Hal Jordan/Green Lantern, Wade Wilson/Deadpool) and Chris Evans (Johnny Storm/Human Torch, Steve Rogers/Captain America), Ron Perlman has already played more than one character in a comic book movie - having portrayed the heroic demon Hellboy in the eponymous movies and the vampire Reinhardt in Blade 2 - so why not give him another shot as Darkseid or Thanos? Perlman is a large man with a deep voice and a strong and prominent jawline, ideal in appearance and sound for roles such as these. The list of voice work he has done for DC and Marvel is quite extensive, having provided the voice of Hulk, Clayface, Abomination, Deathstroke, Batman, Sinestro, Orion and Jax-Ur (amongst several others) in various television shows and video games, so they certainly have a lot of faith in him. As a fairly big name, he would also provide a big draw for viewers.