Many things.

Looking at the trailer, it’s the lost worlds of Sonic before Iizuka’s silly ass “real world” shit took over. Sonic’s animal friends (the ones you rescue from robots) return, the game looks more old school than Generations, etc.

The concepts from Sonic X-treme look to be revived. That’s been a major lost world, and one of the most controversial.

The game takes place on a spherical world, similar to “Little Planet”. That’s a helluva lost world, but I doubt we’ll be seeing the glorious Collision Chaos Zone any time soon.

It seems Sega is honestly taking this long to go back to Sonic’s old school content. It’s too late to appeal to the older fans in an era where he has no appeal. But hey, better late than never. It’s got my interest, in some ways. The problem I see is the villains, really. They’re the worst looking things I’ve laid eyes on in years. And the story is going to revolve around them. What are they, aliens? Mutants? Cousins of Toejam and Earl? Whatever they are, they absolutely SUCK!

I mean, hell, keep everything else. Just get rid of those awful villains.