Oh, I wouldn't skip over Venom. I just think that when you get to Carnage, a serial killer and him not being just a muscle-bound dumb Spider-Man, with a weak reason why they (Venom/Eddie) hate Spidey. You will come to like Carnage better on screen as a character. As a screen presence he would easily dwarf Venom. Keep in mind, I'm talking about these characters in film form, with a well written script.Carnage would be pretty good on film, but we'll never see him, imo. You need Venom to use Carnage and that'll just take too much time to bring in those villains because I highly doubt we'd get both symbiotic villains in one film.
We have seen many serial killers on screen, my personally favorite is from Silence of the Lambs. Just imagine if you will, if Hannibal had the symbiote. Where he can't be contained, he need not hide what he does, and can't be stopped by the police or FBI, even if he's in their front yard. I would love to see how Spider-Man handles a villain like that in live action, especially mentally, who's not out specifically for him, fame, power or money. You don't need to go too deep when it comes to a serial killer, they are their own evil made real that we don't understand. If you do, you'll end up with a story like the Hannibal Rises prequel. Which was horrible. I don't want to know too much about a serial killer, the story lies around the people Carnage would effect. It's why Carnage should not be written with complexity like one would expect from Norman/GG or Octavius/Ock.
Eddie Brock is weak link here for me, no one seems to be able to make that character real, without him seeming like a gimmick for the symbiote. He needs to be retooled, before I would want to see any symbiote on screen ever again. I love the symbiote on Spider-Man in the comics and cartoons and should have felt the same way in SM3. I despise it when it's given to Eddie Brock knowing his horribly written hate for Spider-Man. It's not the celestial costume that I don't find grounded or interesting, it's his character.