Realistically if the 2000s never happened, Sonic would be around the same level of popularity as Chibi-Robo. He'll be fondly remembered for being a great series that was left dormat due to the existence of Puyo Puyo, Yakuza, and Phantasy Star. But then gets revived in the 2010s due to the retro boom scene. Which may seem exciting as first, the Sonic fanbase(Which is extremely niche due to later generations never growing up with Sonic) will complain about how they're not good at all when compared to the originals and they'll sell poorly worldwide. Which leads to Sega killing the Sonic series for good as they go back to focusing on their three popular IPs.