The idea of Classic Sonic really pisses me off.

Classic Sonic is bullshit. Not saying he's a bad character, but Sonic Generations has to completely screws up the story. Saying that Modern and Classic Sonic are two different people from different dimensions makes sense, but there's no point making such a silly plot point if Sonic is so inconsistent over the years. I understand that in the Classic series, it was Sonic's first in-game appearances, so naturally they wanted to perfect it. But if Sega wanted to pay such high attention to detail on his design, why would they just sweep Sonic's appearance tweaks in the classic trilogy under the rug?

Sonic 1's Sonic has a pale color, like Generations Classic Sonic. Sonic 2 looks like Sonic 1's Sonic but with Modern Sonic's color palette, and Sonic 3's Sonic looks like a mix between Classic and Modern, with his sprites having smaller pupils. Sonic Mania, Forces and Superstars all have the same sky-blue color for Sonic.

If anything, the explanation as to why Sonic has green eyes could just be that going Hyper in Sonic 3&K changed his eyes from black to green, as shown again in the sprites. If Sega is so insistent on explaining Sonic's visual continuity, then what happened to the Soap shoes in SA2? Did he just end up throwing them away?

Visually, Classic Sonic is shorter, has a bigger head, smaller hands and has a rounder torso than Modern. Another point to consider about appearance is the muzzle curve. Yes, it's highly debated and I won't talk about it.

The reason why Modern Sonic was even created was to have Sonic appear more cool and slick, going away from the design of Sonic who was a cute hedgehog with the gift of speed, to a taller, but still short, hedgehog who's entire personality revolves haste in all he does, but confidence.

There's no reason why Classic Sonic can't be cool. Look at Sonic Mania's introduction. Sonic confidently stands on the Tornado and hops off swiftly. Hell, there's even official art of (classic) Sonic smoking a fucking joint. That's what made Sonic so unique. Mario was known as nice, down-to-earthy and a someone who always put others before him, but Sonic was a balance of "cool-ness" with heroic values. He painted a picture of a hedgehog who had that bit of "cute curiosity" to him, but once he got his footing, was very confident.

With him being split into two characters, Classic Sonic is now a mute Mickey Mouse clone, and Modern Sonic completely removes the "cute" aspect of Sonic once Generations came along, giving Modern Sonic a reason to be different from Classic Sonic in a way besides looks.

I do understand that Sonic was initially supposed to be an edgy character who did things in an anti-hero manner, but Genesis-era Sonic has no reason to be different from Modern Sonic.

This is where I inject some headcanon of mine. From here, I treat Modern and Classic Sonic as one singular character.

An in-universe explanation could just be that the power of the Master Emerald had warped Sonic's appearance, the Hyper transformation could have left some chaos energy behind in him, which is why his eyes are green, therefore making him faster from Sonic 3&K to Adventure, changing his style of running. This is if Sega really wanted to explain the change from Classic to Modern Sonic.

What Generations could have done was to send Sonic into the past once Eggman started to play with the Time Stones again, and ended up changing the universe, causing some sort of reality shattering anomaly to happen. Sonic has to travel before Current-day Eggman screwed with time.

All in all, Sega didn't need to explain the whole Classic and Modern feud. They could have just said it was a stylistic choice.

You can disagree with me in the replies.