After the 2000's were filled with mostly bad games, Sonic's future(as well as Kirby's at the time) felt extremely bleak. Then came Colors and Generations, a revival attempt that actually worked, unlike Sonic 06. And just last year, we got a glimpse of 2 games that might even top those. Sonic Mania and Sonic Forces. Let's go over their trailers.
Sonic Mania - Following the effort to modernize Sonic, there was a lot of confusion and stress. Fans were angry about Sonic Boom and Lost World. But then Sonic Team realized: "You know what made Sonic Generations good? The fact that we had those 2D parts!" Notice how Generations is generally regarded as the 2nd best Sonic game. So, following this 2D formula and an urge to go back to simpler, more fun gameplay, Sonic Team almost had their game ready.
You know the saying "SEGA does what Nintendon't"? This saying couldn't be more true as of now, because Sonic Team actually handed Mania's development to hardcore fans, who have worked tirelessly on mods, or revisions. Nintendo just removes all fan content on the basis of copyright infringement. Sonic Mania looks great, and seems to follow the original trilogy, as well as CD. This game highly emphasizes on being a callback to the past, even using old art and classic styles of cartoonish animation. The game itself also seems more varied, having cool obstacles like radio signals and popcorn exploding.
Sonic Forces - Following Generations, Sonic Team knew they had a hit formula. This time, the story is much more dramatic and urgent. The trailer begins with giant robots the size of sky scrapers crushing buildings and incinerating entire streets. The game also brings back Classic Sonic, a much beloved character. We don't see much from this trailer, but we do know that the boost seems to be back as well, something that made Sonic Colors and Generations quite fun. Later on, it was revealed we would have 2 new characters, 1 good and 1 bad. Other than that, not much can be deciphered, but we can feel comfort in something that is basically a sequel to Generations.
Edit: The game sucked.