Sonic Generations first hit the PS3, Xbox 360 and PC platforms and every Sonic fan loved the game (of course i couldn't get the game because firstly, I didn't have a 360 or PS3 and secondly, i do not play PC Games because i'm not allowed). In late November, Sega released a 3DS version of the game, but it didn't live up to people's expectations and i will explain why.
people thought that because the Modern Sonic stages were in 3D, then the 3DS Modern Sonic stages would be in 3D as well. Sadly, this isn't the case as every Modern Sonic stage is 2D like the Sonic Rush games which is disappointing seeing as they could have used the 3D to their advantage. another let down is the short length of the game, i'm serious about this, the game can LITERALLY be completed in about a day. Though I did have a lot of fun playing it in that short experience.
the positives about the game would have to be the music in the stages, the depth of the 3D, the colourful environments and the online multiplayer which is something brought back from the Sonic Rush games (which is good because i don't know how to connect to Wi-Fi on DS games!!). i also like the fact you have your own customizable profile cards that lets you choose your favorite Sonic game, Favorite Sonic character and how long you have been a Sonic fan.
Sadly, the shortness of this game, the 2D only option for levels thing is very underwhelming, especially for people who wanted a full 3D Sonic game in 3D environments.
My overall opinions are that if you have a PS3, 360 or PC, then get that version instead but if you are looking for a casual Sonic game on 3DS, then this is your game.