Maplestory and Roblox from ages 9-13 for sure
I'm gonna count the entire Megaman franchise as just one lol, from like 3-12
Endless Ocean: Blue World, somewhere between the ages of 9-12
And once again, a whole collective, but flash games as a whole were huge to me at the same time https://twitter.com/jakeregal/status/1260449257821216768

special shoutouts to TF2, which honestly could replace either of the last 2

and Terraria, which I still play to this day, and while it's probably my favorite game, I wouldn't call it as formative as any of these

I feel like elaborating on all of these because I think this is really interesting :3
Maplestory is by far the game I have sunk the most lifetime hours into, and was *huuuuugely* influential on my music taste, aesthetic, and now that I think about it, I probably liked the cute---

aesthetic as a means of gently rejecting masculinity in an acceptable way

but overall maplestory was an absolute obsession of mine, and it's kinda funny how I never even reached max level even though it consumed my life for so long

Roblox was absolutely the biggest part of my socialization growing up, and was the game I would always play with my IRL friends
but at the same time, it was a game that was deeply important to me, and I would switch between long swatches of maplestory or Roblox at a time---

I think the game really inspired me in a lot of ways, just because of the sheer endless customization and ideas presented.
I remember I would always look for the most obscure levels, trying to find creative, if unpopular concepts that the public didn't know about

Megaman was my childhood series.

I grew up with a PS1 and a PS2, and I don't think I ever played a single "classic PlayStation" game because I was too busy with megaman 8, megaman X4-X8, megaman legends 1 and 2, and pretty much every megaman series but Zero for some reason---

I don't think I made megaman OCs, but my superhero character I had as a kid: Phoenix, was absolutely inspired by megaman X's general aesthetic and concepts, and it really seeped it's way into my favorite concepts

Endless Ocean: Blue World was my most played Wii game, and singlehandedly inspired me to pursue marine biology for a solid 3 years, which is a long ass time for an undiagnosed ADHD and dysphoria riddled kid
I loved discovering every corner of this game and seeing every sight~

Flash games were a huge part of my childhood!
They were super accessible, there was a huge amount of variety, there were constantly new ideas being made, and they even invited multiplayer socialization
pretty much all my casual free time was spent on kongregate

TF2 was simply huge, but it's kinda hard to put into words
I dunno, it's where I started to really try to put skill into games?

also Terraria actually was pretty formative, because it was a micro-obsession in high school, which let me survive depression filled days

also HOLY SHIT I FORGOT ABOUT CHRONO TRIGGER THAT GAME WAS WAY MORE IMPORTANT THAN ENDLESS OCEAN WAS AAAAAA

also shout out to brawl which not only was important to me as a game, but also introduced me to brawl in the family, which led to forums, which led to the internet overall