I grew playing the Sonic games on the GameCube, so that's how I became a Sonic fan. However, I never really considered the whole idea of self-insertion into the Sonic series. One of my friends did sort-of do that, and I noticed how rabid the fanbase was with it when I grew older, but I never really saw the point of self insertion in something like Sonic. Stuff like Stargate and Star Trek I thought about being a cool idea because, well, you're stepping through a f***ing stargate or go trekking across the stars with Spock or Neelix. And, outside of daydreams, I never really saw the whole idea of creating a "self insert" story.
As for today, with my current attitude, I have commonly considered the idea of self-insertion in some of stories I want to write (Whether it be just a quick quip or an almost complete copy). However, I have realized that the problem with that is that I'm full of flaws and that no one thinks like me, except for me. So then I have to find a way for the character to have a damn good excuse as to why they would make such a statement similar to my own, or actually take note of my flaws and attitude and make sure that my in-story version of myself exhibits the same attitude and flaws, and make sure the response from other characters is an appropriate one instead of how I'd like things to be.
Now that I actually think about it after writing that, I feel like that's part of the reason why some of these people are so rabid in creating their own fan characters in something as carefree feeling as Sonic (Or any other series). It's because they want to use it as a form of escape from their real lives because they don't want to handle the troubles in their own day-to-day lives, so they create these personas in these worlds that they feel safe in because their familiar for them.
Also, I just realize I'm getting into the territory of pointless babble, so...let's see what pops up for the I search "[My name] the Hedgehog". Oh dear god, why?