Yes, I basically agree.

Never got into Sonic so I don't really have any expectation for each new Sonic game, but I'm surprised to see the fanbase as strong as ever even though there had been a lot of terrible reception for these games

I never played any Sonic game (well, actually I think I played it once at a friend of mine's, on a Saturn, but whatever), but Sonic was still one of my favourite characters in my childhood, because of the cartoons. I remember watching them on Jetix (is that still a thing???) lol, and I liked how he was badass, and kind yet playful, and sometimes a bit too cocky for his own good, which gave him a lovely knack if getting into trouble, which just made me love him even more. Couple that with the fact that Tails is just amazingly cute and awesome, Sonic X (I think that's what it was called) was my favourite show during my childhood.

Sonic is too cool to die, most franchises would have been destroyed after something like Sonic 06, but not Sonic, not even Sonic Boom, like I said, too cool to die.

I'd of said Sonic Unleashed is the series low point (although 06 is only slighty better), but yeah to survive these games almost unscared can only mean Sonic is invincible by this point.

I kind of agree. I'm not a huge fan of his, but he goes through a ton of shit constantly and always manages to come back. Not bad.

Sonic is iconic.
The only thing that jeopardize him is his personality because unlike other mascot's its so rooted in culture and time. That being said, that can just as easily backfire, so they need to keep reinventing him.

Sonic fan for life.

He won't die, because at this point, no one is there to replace him.

No AAA developer (Outside of Nintendo - Who already have different portion of said pie) are interested in taking over market share that Sonic has, even if taking those share wouldn't be that difficult, they just don't think it worth the investment.

Yes, Sonic 06 and Sonic Booms are horrible. What game are you going to play instead? If you like that style of the game, you're kinda stuck anyway.

Business that wants to kick out Sonic will need to make pretty huge investment with no promise of reward at this point. So...

I was expecting the argument to be "almost nothing can kill him if he has a ring".

Yes, yes he is. This series has seen some ups and some major downs, yet Sonic always seems to return in some form. Sonic is the very example of karmic reincarnation. To die and be reborn as something drastically different from the previous life. 

The problem with Sonic is consistency. We've seen with Colors and Generations that Sonic Team is capable of making good games, but then Lost World happened.