Sonic the Hedgehog

His voice sounds a lot deeper than usual. I can't say I dislike it...but I am wondering how it will sound throughout the entire movie. I like what I've heard in the trailer so far though. And, funnily enough, I can't really use Idris Elba's Knuckles as a reference point---I got introduced to Sonic through the movies, so that was the first Knuckles I ever heard. So when I heard his normal voice, it sounded so high-pitched until I got used to it!

It's interesting how you pointed out that this movie probably won't be a faithful adaptation of Sonic Adventure 2. I was honestly excited about it---mainly because the other attempt I've seen at adapting Sonic Adventure didn't really do it justice. There are some elements in the X adaptation, like Sonic being mistaken for Shadow by virtually everyone in spite of the footage being clear, that were particularly maddening, and I was worried they would make the same mistake in live action.

Can't help but agree on the Gerald Robotnik thing. It's making me a little worried that the movie, overall, might not be dark enough, since it was Gerald's descent into madness that drove him to plant those fake memories into Shadow to destroy the Earth.

As for Amy Rose being introduced...maybe. It depends. Part of me is skeptical of whether they could introduce her naturally in the same film as Shadow, and I'm thinking that maybe introducing Rouge and/or Omega might be easier to tie into the plot. Though they would need to figure out the issue of 'who's going to talk him out of genociding the entire earth' bit. I was thinking of Jojo, similarly to how Chris did so in Sonic X, but I'm wondering how much of an impact that would have.

A large part of what made Chris work as a human side character in the X adaptation was how he was very close to Sonic--like Sonic's equivalent of Maria. And I think Shadow may have realized it. But Sonic and Jojo haven't had that kind of bond, aside from that cute scene where she gives him his sneakers. So I've been thinking of Sonic talking him down, as a backup-backup plan, now. He had a lot of empathy for Knuckles in the last movie, so I think he'd probably do the best job out of all the characters.

Assuming they'll get to a point where he's trying to murder everyone (Which, they'd better!)

I'm also kinda apprehensive about the potential for Jim Carrey leaving too. Any attempt to recast him would be massively unpopular, and rightly so. The way I've been seeing it up until recently is that they would simply stop making movies once Jim Carrey retired. That it's better for the Sonic series to end on a high note for it to fizzle out. But now that I think about it, there may be potential for another Sonic movie with a different villain. Though they'd have to be very careful about it. There are plenty of cool villains in Sonic---Surge the Tenrec, Metal Sonic, Mephiles the Dark---the main issue is, which villains can be cool without Eggman being there?

I might have an answer. The Metarex arc in Sonic X was excellent, and Eggman was only a minor villain in that arc. I mean, a movie focused on intergalactic robots and explosions that's actually good*? Sign me up!

Though, like I said, they would need to be careful about it, and it could easily suck if they make it too grimdark or goofy (especially since the backdrop for the original conflict involved the genocide/assimilation of an entire planet)

Thank you very much for the detailed thoughts! :) And hopefully you didn't mind getting this massive wall of text! *Not that I'm mad about the last Transformers movie. Not at all!