For years now Sonic gans have followed The Sonic Cycle. It starts with elation as Sega announces that Sonic is "going back to his roots", there will be "no shitty friends". Then the first screenshot comes out showing his shitty friends and some new non classic Sonic Mechanic.
However, with Sonic Generations (and much like Sonic Colours before) the Sonic Cycle has been broken. Shattered if you will.
Generations is a celebration of the past 20 years of Sonic. Featuring levels from the best and Worst of Sonic (1,2,3 & Knuckles, Adventure 1&2, Heroes, 2006, Unleashed and Colours). The game is split into 3 sections: The Mega Drive Era, Dreamcast Era (oddly including Heroes, which never came out on DC) and the Modern Era.
Each Level is split into 2 acts. Act 1 is classic Sonic, Act 2 is Modern Sonic. Modern Sonic plays exactly like the daytime stages in Unleashed and as in Sonic Colours and i'd go as far as to say it's the best they've done with Sonic in 3D yet.
However, everyone knows Classic Sonic is where it's at. I really don't understand how they've done it (especially given their output over the years) but by god they've pretty much nailed Classic Sonic. I say pretty much because there are some strange inconsistencies, such as when rolling down a hill rather than gain momentum all the time, Sonic will just uncurl and stop dead in his tracks on the hill and managing to walk up a steep incline that you really should need some speed for. However for the most part it's as close to classic as we're going to get. (Short of playing the originals).
The best part of the game is easily the soundtrack, featuring lots of songs from previous Sonic Games, and letting you swap any levels song for any other song (which is a genius feature). Personally i do all of Modern Sonic's levels to Sonic Boom, but then i'm weird like that.
There's lots of challenges to complete as well to unlock new songs/skills/artwork, some of which are just unfair (Vector Challenge, i'm looking at you). However, for the most part it is way too easy to S Rank a challenge or a level - some more difficult challenges would be welcome.
The other main problem is the level choice. There's quite a few city levels. Sonic 3 isn't represented at all (ok, Sky Sanctuary is from Sonic 3 & Knuckles, but it doesn't really count). It would have been great to see something like The Doomsday Zone redone or Carnival Night Zone (complete with Barrel). However, what's there is still great, and somehow Classic Crisis City (from Sonic 2006) actually manages to be a really good level (modern is just as broken as it was in 2006 funnily enough).
It's hard not to recommend Sonic Generations, Sonic Team actually almost knocked it out of the park with this, and i think if they'd considered some different levels, maybe added in a few more bosses (there's 3 bosses and 3 rival fights then the final boss) they'd have been onto a winner. Lets hope there's some nice DLC levels for this or maybe even a sequel?