It is a hard one to explain. To be honest, classic and Modern have become their Own things now with Forces rectonning Sonic Generations so that they were alternate counterparts instead of being from different time periods. However, it has not been confirmed that Modern Sonic has “lost” his past from the classic games, nor would it make sense since Modern Sonic showet familiarity with the locations in Generations (you cant just go on record and say that those scenes did not happen).
What is most likely is that past elements has been sealed by Sonic Team so that Modern Sonic cant touch it, like how the Archie Comics could not use certain characters anymore prior to the reboot (we knew they were still there, but they were never going to reappear).
This May be wishful thinking, but officially, there has been no statement saying that Modern Sonic has not been through the classic games (this would be a bad move Anyhow for Sonic Team since so much World building was made in those games)
I made the edit to be consistent with the SNN Wiki's current stance on the issue.
In all honesty though, it's not a stance I agree with. Having two separate articles for "Ray the Flying Squirrel" and "Ray the Flying Squirrel (Classic Sonic's World)" is silly, since there is no "Modern series" version of Ray.
Has anybody noticed that Mighty the Armadillo is missing?
Iizuka: Mighty is a part of the Classic world and the Classic group of characters, and some of the Chaotix did get interpreted for the Modern vision of the games. However, Mighty still exists in the Classic world, so maybe we'll see him in the future in some Classic iteration.
EGM: Team Chaotix's gameplay is quite different than the other three teams'. Why did you decide to bring back these characters and give them fun, silly goals like rounding up hermit crabs?
Takashi Iizuka: In my mind, I didn't bring back the Team Chaotix characters from the past -- instead, they're new characters who happen to fit into the game. I wanted to create at least one team that was totally different from how Team Sonic talks and acts. Those three characters, Charmy, Espio, and Vector... they're so unique in their actions, personalities, and goals. They add a lot of flavor and variety to the overall picture. There's also the fact that those characters have never been used by Sonic Team -- we weren't involved with Knuckles Chaotix; some other internal sega Development team did that. So it's not a matter of bringing up old characters... we recreated those characters from the ground up. We want Sonic to be Sonic, and for the others to be supporting characters. I'm very happy with the way Team Chaotix turned out, so I hope they'll be brought back to another title in the future. You'll see more of them!
As of Sonic Mania and Sonic Forces and Iizuka's statements, I think it would be best to treat all the "black eyed Sonic" games as "Classic Sonic series" and all the "green eyed Sonic" games as "Modern Sonic series".
There's still some overlap - Modern Sonic games have referenced Sonic 1, 2, 3 & Knuckles and CD. So it's not perfect. I kind of think of it like whenever DC Comics reboots its continuity but keeps bits and pieces of previous continuity. So Sonic Adventure would be the reboot, but it brought some elements of Sonic 1/2/3&K/CD along with it, whilst changing other elements (Amy going from age 8 to age 12).
Yeah, it's true that it's unnecessary to have them separate just because of three four games (yes, I forgot to mention "Triple Trouble" and "Chaotix" games).
Therefore that was the reason why I had to reverted, but DeCool had a different reason. If he want to speak that reason, he's welcome to stomping me down and spit on my corpse if he wanted.
And Mighty made his debut in "Sonic Mania Plus" after all, with Ray the Flying Squirrel, as well as "Sonic Mania Adventure" Episode 4 onward.
"Sonic Heroes" made up for all of that. And yes, I agreed - Chaotix team is unique comparing to the rest of gangs in said game. Amy Rose's team covered the "Easy Mode", Sonic Team on "Middle Mode" while Dark Team facing the challenge-est mode. So that left the fourth; "Detective Mode" - Chaotix Team.
Of course, until "Sonic Generations" and "Sonic Forces" had both Sonics shoved in same team, then pop them apart once the story is finished.
Indeed, after all, Modern Sonic still remembered those events that hadn't interrupted by Phantom Ruby. Classic Sonic went in different direction, which is of course, set before "Sonic the Hedgehog 3" event. So you're saying that there will be a new version named "Sonic Adventure Zero", if we followed the code of "Starfox" reboot idea? I mean, such as "Starfox" got rebooted at least twice (first being Starfox 64 and again as Starfox Zero)?
Still, several of Sonic's adventures are still depicted the ones he had before Adventure. We're only separating these articles so as to not take the whole "you're from another dimension" thing lightheartedly. The canon of these games are in a constant state of flux.
So you think that "Sonic Adventure" will get a reboot version, now that Sonic Mania came around, so that they could included Mighty and Ray, along with Phantom Ruby events in their memories? Or SEGA would just move on to new games?
It is also with the regards to the events that could have still possibly transpired in Modern's dimension that articles like Mighty and Ray get separated. If the events of SegaSonic the Hedgehog occurred to both Classic and Modern, then logic would demand that there are two Mightys and Rays. So far, nothing official has stated that the classic games are exclusive to the classic world, meaning that the safest play would be to include two incarnations of those characters.
Iizuka's stance seems to be that Mighty/Ray/Fang/Bean/Bark only exist in the Classic world and don't belong to the Modern world.
His stance on Vector/Charmy/Espio is that the Modern versions are "new characters", who were recreated from the ground up.
Iizuka's stance on Mighty/Ray/Fang/Bean/Bark's situation could just mean that they are not going to return to the modern games after their debut in the classic games. That they are "Classic games only".
Iizuka's stance on Vector/Charmy/Espio was according to what he thought "In [his] mind". Why would he say that if there was not a second opinion to that-perhaps another one more accepted by the fans?