Sonic the Hedgehog

A primarily video game-based franchise, also just called Sonic, about its main protagonist, Sonic the Hedgehog. In it, Sonic runs around at the speed of sound on his journeys alongside his friends Tails Miles Prower the Two-Tailed Fox, Knuckles the Echidna, and many others, stopping Dr. Eggman (formerly Dr. Robotnik) from completing whatever evil scheme he has in mind.

Sonic's Great Decline
There was a time when the Sonic vs Mario argument was real. When Sonic was in his heyday, he used to be on top of the world. But his reputation as 𝙏𝙃𝙀 𝙁𝘼𝙎𝙏𝙀𝙎𝙏 𝙏𝙃𝙄𝙉𝙂 𝘼𝙇𝙄𝙄𝙄𝙄𝙄𝙄𝙄-𝙀𝙀𝙀-𝙄𝙄𝙄𝙄𝙄𝙄𝙄𝙑𝙀 came crashing down around him when the 3D Sonic games came out. The most infamous of the lot is Sonic '06, a game that was meant to be a celebration of Sonic's tenth anniversary, but it was so plagued by bugs, glitches, and general unplayability that it only became popular through how poorly programmed it was. Overall, the games after and including Sonic Adventure are regarded as glitchy, slow (in terms of Sonic's movements compared to his lightning-speed racing in Sonic the Hedgehog 1, 2, and 3), and straying from what made Sonic so great when he was at the peak of his popularity. At the same time, Mario, a franchise that people say hardly or never pushes out a bad game, continued to ride on its success with no end in sight, which makes Sonic's failure even worse.