If there was a man named Call of Duty, I'd name him just as resilient.

But in all seriousness, as someone who kinda hates Sonic, it is pretty impressive that he's still alive after catastrophes such as Shadow the Hedgehog, Sonic 06, and Sonic Boom Rise of Lyric.

I guess it's cause games like the original triolgy on Genesis are just so iconic, Adventure 1 and 2 were pretty impressive at the time, and somewhat more recent games like Colors and generations got pretty good reception, with Generations being my fav Sonic game of all time, so whenever Sonic games are good, they stick out.

Also, the Sonic fanbase is easily one of the more crazier fanbase out there, and if the series were ever to be stopped, no doubt that there would be bloodshed throughout the entire internet.

After all this years, it's still the face of Sega. And as long as Sega is around, it won't go away. Also, it has almost as much nostalgia-power as Mario.

Yes. Heres why: Sonic is the only character who's game design is still his own. Where else can you find a game like Sonic?

Tons of mario clones
MegaMan clones
Castlevania clones

But how many Sonic clones? If you want high speed platforming Sonic is still the only place to get it. Thus his value is retained unlike something like all these shooters and open world games which all offer the same experience.

This.  It's amazing that Sonic just keeps going, and not in a fad way like Ninja Turtles do by poping up every 4 to 5 years just to go and die again for the same amount of time.

The fan base is utterly bananas and kids always like Sonic.  Also it might be something to do with how Sonic keeps changing in art style over the years.

1991:

1998:

2006:

2013:

I suppose he changes with the times and keeps finding a way to fit in and stay relevant.

Cooler than the earth is blue.

Bahamut from FF has been f*cking with me for nearly 30 years.

Plus special mentions need to go to:

and...

Perhaps the nature of the Internet keeps sanic Sonic going too.

I would never leave Sonic side. If I had to choose between FF15,S05, Shenmue 3, FF7R, Legend of Dragoon 2, Legaia 3, DQ11, Crash revival,or Sonic.. I would choose Sonic. 

Personally I like the 1993 Japanese Sonic CD Anime style.  This is what needs a come back:

I think that's fair.