time gear
Eternity in an hour
I think that the modern games and the classic games are equally good, just for entirely different reasons. They initially tried to stick to the classic formula with the Adventure series, trying to translate it into 3D, however they eventually decided to stop trying to do the same thing over and over and wanted to make the games more unique, unbound by what had come before. This I think is the primary reason why the series has departed so much from the Genesis/Mega Drive era. They never really abandoned that style, they've always returned to it from time to time. The Advance series, Rush, Generations, etc. They just don't want the series to all be the same, or at least they didn't. Ever since 06 they've been increasingly afraid to go against the fans, trying to play it safe as much as possible. Unleashed was fairly successful, which is why they've gone back to that formula so much.
The classic series excelled at momentum based gameplay in which speed was earned, and if you knew what you were doing you could keep it up. The generally downhill level design mentality allowed for this if you stuck to the right paths, you could keep your speed going without having to fight back against the level design most of the time.
The modern games have generally tried to make other gameplay mechanics more central, with speed either being handed out like candy or focused less on in general. Heroes was all about the team mechanic, Shadow focused on mission objectives, etc. They acknowledge that Sonic is fast, but are trying to be more than just speed based games. Even the boost games which hand out speed like candy are trying to do something entirely different from the old games.
This is generally where the big rift in the fanbase comes from. People argue about which is better when they should really be appreciating both halves of Sonic for what they are. The classic fans want the modern games to be more like the old games from back in the day, while the modern fans appreciate the gimmicks brought forth by each of the newer games and wonder how the classic fans could be so stuck in the past. This is largely a result of people growing up in different decades. Not enough people realize that there's value to both the modern and classic Sonic games, and that a game that incorporates elements of both can work if handled correctly.
A lot of the fear, I think, comes from SEGA's recent attempts at merging the two together. While Generations is generally seen favorably, even that game has it's issues, shortcomings, and missed opportunities. The less imaginative among us have a hard time imagining how anyone could do a better job. They see classic and modern as being unable to mix together, they see games in general that try as being worse off for it. They demand that games embrace either classic or modern entirely, without veering too close to the other. It's such a limiting mindset.
