With each new Sonic release they celebrate it as if the series has what it takes to stand up the rich and diverse history of Mario.
Most Sonic games are pretty much the same. With the exception of Sonic Adventure 1 and 2, I basically feel like all the 3D games are simply a matter of steer clear of this, jump now, hit that, repeat, and the 2D series is pretty much the same thing, only with each sequel adding in a new gimmick that never quite stacked up as nicely as the diverse set of suits and vehicles that you always had at your disposal in the Mario games, and which always changed the game play DRASTICALLY.
Sonic 1 was fun because it was unique then, and it was not created for Sonic perfectionists yet, so it was playable without dying and loosing your rings constantly. The later sequels began to all feel the same to me despite their gimmicks, and more than that I found my self not caring to see what the next level or "zone" looked like at all. It just wasn't the same as being in the early 90's, wondering what Sega was going to make their home console do next. As far as I am concerned, the series looked the best and had the best levels (in 2D format) with Sega CD. Not only did I like the future dystopian theme, not to mention all around dark them of the game all together, but there was something truly sinister about the robotic Sonic in that game, the art direction was not cute and pastel as all video game art has became since then, and it's really a shame as it's hurt the Sonic series, just as it has plagued Phantasy Star and other once legendary video game series. Having said that though, I can't see the Sonic Adventure games working if they were not cute. Granted the cartoon series sucks and since they are keeping in theme with that, it lends to a bunch of characters and a plot you don't care about, but they games are solid, and as far as Sonic games are concerned, they are the one's that actually try to be unique and diversify the game play, especially in part 2.
Anyhow, Sega should give it, that or TRULY go back to their roots, when they were dark, but alas, it's not even the same developers, team organizers, artists, etc. The glory days are over and Sonic needs to step aside and make room for Alex Kidd or Wonder Boy in all it's Metroidvania goodness!