If you grew up with Sonic since the very first game, you're probably a big 2D Sonic fan. If you jumped into the series with Sonic Adventure, you probably enjoy the 3D outings more. While Sonic fans certainly appreciate both sides of Sonic, most have a style they favor over the other. Whatever version of Sonic you like better, no worries. SEGA has plans to support both of them.
In an interview with Otaquest, SEGA's Takashi Iizuka talked a bit about 2D and 3D Sonic. He makes it clear that both are very important to SEGA, and they plan on paying attention to both moving forward.
Not much time has passed since the distinction between “classic” and “modern” was made, in fact, it was since 2011’s “Sonic Generations” title. Even before that, in addition to the main 3D series, there was a high demand for the 2D action games such as the Sonic Advance series, so we revived the old Sonic as Classic Sonic for the 20th-anniversary title, Sonic Generations. We initially thought that it would be a 20th Anniversary project only, however after that we had a strong demand for a new classic Sonic standalone title, that became 2017’s Sonic Mania. We would like to take good care of these two very popular iterations of Sonic’s in the future.