Drop dash seems like the best thing you could add to a 2D Sonic game, why hasn't this been done before?
Not sure i like the top speed running animation but it seems to switch to the old style for the rest of the trailer, so i'm not sure what's going on there, regardless i'll be spending most of the game spinning.
Edit: After re-watching the trailer, re-imagined classics stages and new zones, will the playable characters and drop dash ability be usable on classic stages? I can think of a few zones where that move would be suicide.

Didn't they try a return to 2d with "sonic 4"? Now they're just doing a return to 2d with genesis-level graphics. Even the trailer is admitting they're trying to figure out what made Sonic popular in the first place since they don't even know.

I'm not saying the game's going to be bad or anything, it's just clear they're struggling. Personally, I liked Sonic Generations a lot, most recent Sonic game I've really enjoyed, and it was because the 3D levels weren't horribly clunky (and even had 2D sections in them) and the 2D levels were actually 2.5D and generated with 3D graphics. My only gripes were Sonic as the only playable character, and no multiplayer. Oh and the cutscenes and story were awful, but at this point you pretty much expect that from a Sonic game, that it's going to be a really bad Saturday morning cartoon. Other than that, Sonic Generations really nailed it out of the park, for me. THAT'S what they should be returning to, honestly.

I tried Sonic 4, but something about the level design was just annoying to me, and I couldn't really get into it. I didn't beat Episode 1 and other than just to see what Tails looked like I haven't played Episode 2. =/

I liked Generations, though the jump in that game always felt too short, apart from that it was a huge improvement over Sonic 4 which just wasn't good, it was also trying for the fairly new trend at the time of being episodic... which might have been ok if the game was good but it wasn't.
Where Sonic 4 was supposedly trying to be the next great sequel to the franchise, this is trying to be a fun nostalgia trip, mixing classic zones with new stuff in the 16-bit style we know and love. If they can get it right it should be fun.

I feel like Sonic fans all identify themselves with certain parts of the franchise, this is me:
Almost all the 16-bit music
Sonic & Knuckles
Sonic 3D Blast
Sonic Adventure - I love its soundtrack also
Sonic All Stars Racing Transformed - Easily my favorite kart racer
And being of the opinion that Sonic isn't all about going fast, but of platforming, jumping on enemies and having occasional short roller coaster "rides".
I've enjoyed other games in the franchise of course, but those are the parts i like most and will defend :P.

Worth noting the developers are from three different indie parties, so they're the ones figuring out how to make a new 2D Sonic work. The Sonic Team has virtually no involvement with this game. On the other hand, that means The Sonic Team has time to work on a new 3D Sonic game, which has been announced on the same day (at the end of the livestream anniversary celebration). Dubbed Project Sonic 2017, they showed a teaser video showing a character that reminds us of one game (one where I see some of you mentioned so they HAVE been noticing our demands) and an environment that reminds us of another Sonic game. They then showed a release window of Holiday 2017 (which I doubt they'll reach, so expect a delay to 2018) along with the Sonic head silhouette since they don't have a title. Please note in the livestream they clearly emphasized that Project Sonic 2017 is not a sequel to any game, but rather a brand new experience. This wasn't even translated. The Japanese guy said it in plain English.

I can't get the video to work with the yt tag, so I'll just paste the link below: