You're right - Metal Sonic's not a flawless argument because Fighters and R cause problems. Those can be considered to be on the same level as Mario Kart in canon though, so it's not too big a deal. I don't think Metal Sonic not having a fight with Sonic is a way of saying he's inferior to Mecha Sonic - the attacks Metal Sonic does have (a boost and a shield) are a lot more advanced than what Mecha is shown with. Mecha Sonic also needs to wait a lot of time before actually attacking and it leaves him open to attacks, yet Metal Sonic doesn't need to do anything of the sort and can actually attack while moving. If the Mecha Sonic in Death Egg Zone was just an improvisation or a way to stall Sonic, why is Eggman watching the fight just outside the room when he has that really big Death Egg Robot sitting in the back? No it doesn't. That means he created the smaller and more advanced Metal Sonic and two big clunky Mecha Sonics - that's like a PS4 and two Ataris. The Mecha Sonic in 3K you could definitely argue for being a prototype though, considering it's thrown in with a bunch of old machines and left behind after the events of the game. I really like the idea of Eggman slowly getting closer to his own robot Sonic as the Classic series goes down, going from a loud and simplistic S2 Mecha Sonic to a robot that's even capable of emulating Sonic's finger-wagging. I think the the Death Egg plot fits perfectly as being the point that made the world first notice Sonic as a hero, which attracts Amy to him and in turn allow Sonic CD to happen. There's a kid in Station Square who talks about Sonic saving the world, as well as asking about Angel Island - which was somewhat of a legend up until S3K (and still generally unknown considering the Mystic Ruins guys didn't know what it was). Just because Tails wasn't in Sonic CD doesn't mean that it has to be set before Sonic meets him - By that logic, CD has to come before Sonic 1 because Eggman isn't using Animals to power his robots.