I could see Vin Diesel doing well as the Shocker.
I'm still a fan of Oded Fehr as Kraven, due mostly to his exotic look and his size. He could convincingly come off as a foreign Survivorman-type hunter looking to take down the world's hardest prey.
For Carnage, I like the idea of Eric Stoltz. He's got the creepy criminal/paedophile vibe going for him. Well, I guess it doesn't really help HIM out, but the characterization would be pretty good.
We're all pretty unanimous in our support for Bruce Campbell as Mysterio, eh? I don't know though, he seems better suited to having a scene-stealing role every now and then rather than being the main villain. Plus, he'd be too recognizable from the previous films.
I hope I'm not alone in thinking Elisha Cuthbert would make a not-bad Black Cat... she's not the world's best actress, but she doesn't really have to be. She could be sultry and sexy.
For Electro, I'd like to see a little nerdy guy... maybe J.P. Manoux, who's currently on ER as the dickweed surgeon.
Rhino, I like the idea of Dominic West.