Is it possible for an opinion to be WRONG?!?
Just kidding. Some of your choices are... interesting. As a matter of fact, I haven't heard anything quite as "interesting" as choosing Jason Statham as Saint Walker since someone tried to convince me that Arnold Schwarzenegger should be cast as Superman (to quote their reasoning, "Can you imagine that 'S' stretched over his chest?!?").
Kyle Rayner - Zac Efron is fine, I guess. Generic young guy kinda thing.
If I were making a movie of this, though, I'd go in a completely different direction and eject Kyle Rayner (despite being a fan) and go with John Stewart for the role. Thanks to JLU, that character is arguably the most familiar for audiences (yes, even despite the movie). So, I'd probably do...
John Stewart - Donald Glover.
I went young. I think that Glover could handle the role. Plus, I'd kinda like to see how he'd handle a less comic role.
Glomulus - Yeah, CGI, but I always hear Howie Mandel doing a Bobby/Gizmo sorta voice. Or maybe Andy Serkis, who did the voice of Gollum in the Lord of the Rings.
I'm afraid casting anyone that voices for The Simpsons would immediately make people think of The Simpsons.
Bleeze - I'd go with Mila Kunis.
Pretty sure she could play rage well.
Fatality - I'd have to go with Gugu Mbatha-Raw.
I've liked her in everything I've ever seen her in, and, in some of those things, she was the ONLY thing I liked. Mayhaps the most beautiful woman in the world.
Saint Walker - Doug Jones.
C'mon, this was a given, right? Of all these choices, this one was near instantaneous for me. Everytime I read Saint Walker in the comics, he sounds like Abe Sapien from Hellboy 2. Plus, the guy kinda has that hollow-eyed other-worldly look to him.
Munk - Generic popular wrestler of the moment.
Seriously. Take whichever wrestling guy that can draw anyone to theaters and put him in a role that demands little more that uttering the occasional "Nok!" (Mickey Rourke, unfortunately, would go all method on this role and go live in the jungle for six months before filming, developing his own "Nok" intonations, coming up with an entire language.)
Arkillo - Again, CGI, but I'm going to go with a voice actor for this one. Specifically, Kevin Michael Richardson.
Richardson had the unfortunate task of NOT BEING Mark Hamil and voicing the Joker in "The Batman" (the non-Timmverse cartoon from around 2004) and more recently was the voice of Panthro in the Cartoon Network update of the Thundercats. His version of the Joker was a pretty radical departure, with a lot more range in tone, from high pitches to deep, guttural rage, very over-the-top. I think his guttural range would go great with Arkillo.