For whatever reason, in the middle of the night, I couldn't help thinking about what order the Sonic games were supposed to have happened chronologically. For a series that only really gained any kind of "lore" a decade into its run, Sonic's chronology gets pretty damned complicated. Mostly because the series was never created with any kind of grand continuity in mind, so the games kind of just did whatever.
For the fun of it, I decided I'd try to figure it out for myself. Note that, for interdimensional copyright reasons, I'll only be citing games made up to the point in time that I'm sending this back to, so there's that. Also note that no matter what I say or do, things won't always line up neatly, so expect a lot of conjecture. You're free to disagree on any of these points.
Tails Adventure (GG)
The beginning of this timeline is a tad vague, but I'm putting Tails Adventure here first because the original Japanese manual places it in a time before Sonic and Tails first met, and the way Tails speaks in said manual's little short story sounds a lot more infantile than we're used to hearing from him, thus implying this game takes place a significant amount of time before then. Not to mention, said manual cites the island the game takes place on as being "the place where Chaos Emeralds lay dormant since ancient times", implying this takes place before even Sonic 1.
If you're wondering why I went with the Japanese manual, this is because Japan's internal lore for the games tends to be more consistent, and the idea of this game being a prequel makes more sense when you consider how Tails controls in this game. He waddles around like he barely knows how to walk, and doesn't know how to spin attack or use his tails to accelerate. Why wouldn't he know these things, if he'd already been adventuring with Sonic for some time?
Sonic the Hedgehog (Genesis/Mega Drive)
This one's a no-brainer. What's less of a no-brainer is what to do with this game's 8-bit counterpart. It's different enough that it could be a separate chain of events, but it also has just enough overlap at times that it could be a different telling of the same events (which is something we'll be seeing a lot of, from Unleashed onward). For simplicity's sake, though, we'll just say that the 8-bit game takes place some time after the 16-bit one.
Sonic the Hedgehog (SMS/GG)
Before we go on, I want to point out that we are NOT factoring either of the Sonic kiddie rides. No Cop Sonic for you guys; it's canon that Sonic doesn't have a house, so it follows that he can't/won't hold down a job in the first place. Also, be real: who the hell WANTS Sonic to be a cop? That's kind of his antithesis.
This one's a tad contentious, but this one most likely starts some time before Sonic and Tails first meet, but the rest of the actual game takes place all throughout time. The way I see it, if Sonic and Tails knew each other by this point, why wouldn't Tails have come along?
SegaSonic the Hedgehog (Arcade)
Alright, there's no particular reason I've put this one here specifically. As long as it takes place at any point before Sonic 3, we're gravy.
Sonic and Tails first meet.
Sonic 2 (SMS/GG)
The reason I'm placing this one before its 16-bit counterpart has to do with the number of Chaos Emeralds in it. There are only six, so it makes sense that this takes place at a point in time where Sonic and Robotnik only know about those six. Of course, as we'll see later, this theory might not hold up the best.
Again, only six Emeralds implies that these six are the only ones the characters know about. Also, note that Tails can't enter the Special Zone in this game, yet he can in Sonic 2 16-bit. It's likely he just hasn't learned how, yet.
I don't believe this game even has a plot, but it might as well go here. Both Tails and Amy are here, so it would probably take place around this point in time, assuming it happens at all.
Okay, so this next one is definitely going to give a lot of people pause, but bear with me. I swear I'm not doing this to try and shock people or make my list "out there" in any way.
Sonic Triple Trouble
No matter how you slice it, this game's tricky to place. Arguably, you could consider it a different telling of Sonic 3's events, but there's too many differences in the narrative to warrant that, and Nack/Fang does show up again later. Also, whether this is Sonic's first time meeting Knuckles doesn't particularly matter, since either way he fell for the same trick twice (and two more times in Adventure and its Pocket counterpart). I'm again putting this here before Sonic 2 16-bit because there are only six Emeralds in this game.
Sonic 2 (Genesis/Mega Drive)
Again, no-brainer here.
Now, I'm sure you're all chomping at the bit to know when Sonic Spinball is supposed to take place. Well... to be blunt, it's not canon to this continuity. I'm not saying this because of any official statement, but because it contradicts too much of the rest of the series: there are sixteen Chaos Emeralds, all of them are the same color, Sonic never becomes Super Sonic after collecting them, characters from SatAM and AoStH both make their only appearances in the games here, the list goes on and on.
But, you know else what I can make all the same statements about? Archie Sonic. That's right, I believe Sonic Spinball takes place in the Archie Sonic universe. Note the designs used for the SatAM characters, Sally's especially lining up with what the comics were going with at the time.
Note too that there were far more than seven Chaos Emeralds at the time in the comics, and they were all the same green color (close enough).
And, there was a Spinball tie-in comic that implies itself to be a prequel to the game, and is undoubtedly canon to the rest of the comic (Hip and Hop show up later). So, there you have it:
Archie Sonic #6 happens, then Sonic Spinball takes place, and the games' continuity remains untouched.
Sonic 3 & Knuckles
This happens pretty soon after Sonic 2, I figure. Sonic's campaign happens first, and Knuckles' soon after. There's a few telltale signs in Knuckles' route that show this, such as Angel Island already being afloat in the ending.
Sonic 4, all three episodes
It's stated to take place directly after Sonic 3, so obviously it goes here. As for Metal Sonic having lain dormant on the Little Planet since Sonic CD? I'm going with the idea that the Metal Sonic seen in Triple Trouble was a different unit.
Sonic Generations (Classic Sonic's perspective)
And here's where shit gets very complicated, very fast. Now, the first thing to note is that Modern Sonic and Tails have no memory of the events of Generations despite their Classic counterparts being present. You know what that means? Yep. It's a Timeline Split!
Whoa, Nelly! Thankfully, covering the new Classic Sonic timeline is simple enough.
Classic Sonic Timeline
Classic Sonic and Classic Eggman make it back to their new timeline, each having learned new things that cause their actions to diverge from Modern Sonic's timeline.
Sonic Mania and its Encore Mode
Sonic Forces (Classic Sonic's Perspective)
Sonic Mania Adventures
That's about it. Now, back to:
Original/Modern Sonic Timeline
Sonic Drift 2
Again a matter of whether you think this game even happens in the first place. The fact that zones from Sonic 2 and 3 show up here imply that this takes place after those two games.
This one's a tad tricky, but I'm putting it here because Heavy shows up here, and it would make more sense for Eggman to still be using Heavies in Sonic Mania if it takes place in a timeline where they haven't betrayed him.
This one could take place just about any time between Sonic Chaos and Adventure, so it might as well go here.
This one probably takes place around the same time as Skypatrol, since Tails is absent.
Sonic the Fighters
This one can take place pretty much any time between Sonic 4 and Adventure, so I'm putting it here.
Sonic 3D Blast
As an aside, I don't think I should have to say it, but Sonic's Schoolhouse and all the other edutainment games I neglected to mention don't fit anywhere, and thus don't go here.
After this, Sonic and friends go their separate ways for a while, as implied by the frequent use of "Long time, no see!", and Amy's reminiscing in Sonic Adventure.
All right! Finally, the Modern era begins in earnest. This is the point in time where the games start to have a real narrative, and thus the point where tracking what takes place when is a tad easier, since the series loves to reference earlier events. Despite Sonic 4 using the same designs introduced in this game, it's implied both here and in later games that their new appearances are a sign of the cast aging.
Sonic Pocket Adventure
I'm putting Advance here, since the final boss takes place on the Moon, which at this point is still whole.
Sonic Adventure 2
Sonic Advance 2
Sonic Pinball Party
Here's where things get a tad tricky. This is the game where Shadow comes back, so obviously it happens before his appearance in Sonic Battle... But so does the next game!
Shadow the Hedgehog
This one happens soon after Heroes, because Shadow is still amnesiac here.
Now that Shadow remembers everything, his behavior here makes sense.
Sonic Advance 3
Now we're about to hit a major Gordian Knot in this timeline, so bear with me on this one.
So, the starting point of Sonic's campaign happens before Sonic Rush, but for Blaze, that game's already happened, since she knows who Sonic is, but he seemingly doesn't know her. She is indeed from a different dimension altogether, but somehow ended up in Silver's future. Then, of course, the ending undoes everything that happened in this game, so it never mattered anyway.
UPDATE: An alternate theory has come to my attention that still places this game in the same spot in time, but for different reasons. Please give it a look here.
Sonic and the Secret Rings
Sonic Rush Adventure
Mario & Sonic at the Olympic Games
Given that it's mentioned in that interview I linked, and no sign is ever given of it being non-canon... Yeah, somehow Mario and Sonic's worlds have access to/are(?) the same Earth. Just go with it.
Sonic Rivals 2
Sonic Riders: Zero Gravity
So, let's get one thing out of the way: because of Ken Penders being a fuckboy, Sonic Chronicles is non-canon. Fuck you, too, Kenjamin.
The two distinct versions of this game are essentially two different tellings of the same events.
Mario & Sonic at the Olympic Winter Games
Sonic Free Riders
Another game where the distinct versions are two different tellings of the same events.
Sonic Generations (Modern Sonic's perspective)
Same deal as Colors, and of course this is where we see the other end of that timeline split.
Mario & Sonic at the London 2012 Olympic Games
Sonic Lost World
I wish this wasn't canon, but it is.
Mario & Sonic at the Sochi 2014 Olympic Games
Mario & Sonic at the Rio 2016 Olympic Games
S'cuse me while I chuck my chili.
Mario & Sonic at the Olympic Games Tokyo 2020
And that's all I can legally put here, for now. Any comments or corrections you might have, please direct them at my guestbook.