While not quite as satisfying as the HD versions, Sonic Generations 3DS is a fun version in its own right.
The story found in the HD versions of the game is roughly the same in the 3DS. Sonic accidentally spoils Tail's plan to throw Sonic a surprise birthday party, when all of a sudden a mysterious entity known as the Time Eater sends Sonic and Tails into a white void. There, Sonic meets up with his younger Genesis-era self (a.k.a. Classic Sonic), as well as Classic Tails. The two Sonics team up and travel through seven iconic worlds found in Sonic's past. The story being incredibly basic isn't really an issue (most Sonic games have never been about story), but the problem is that the cutscenes are very basic. It only shows off a couple of characters on screen as they show basic animations and give out the occasional grunts and single bits of dialog. The 3DS is perfectly capable of presenting cutscenes and voice acting, so why not take advantage of it?
Gameplay involves two acts per stage. Act 1 represents Classic Sonic and Act 2 represents Modern Sonic. Classic Sonic plays pretty much as you would expect at first, but very early into the next set of stages that quickly changes when he is taught the homing attack. If one is a purist, most of the levels are designed to where you don't need to use the homing attack; but the fact that it is permanently there makes you tempted to use it regardless. Modern Sonic's boost-heavy gameplay is largely similar to the Sonic Rush titles on the Nintendo DS, though this time the camera will occasionally shift angles to give a slight 3-D look despite the fact that you are still locked onto a two dimensional plane. When you start out, both gameplay styles seem a bit redundant; but once Classic Sonic gains the homing attack, having two Sonics seems absolutely pointless since the only thing that truly separates them is a boost feature and a spin dash.
Despite the gameplay styles being redundant, the levels are fast-paced and fun to blast through and both Sonics control nicely. The multi-layered levels are designed rather well for the most part, but the game does have a few cheap enemy placements that can stop the action dead unless you memorize the levels. The stage selection is nice, but there definitely could have been more added to the selection.
As you progress through the story or if you have Play Coins, the game also offers missions to unlock which offer a bit more meat to the gameplay. The challenges range from destroying a certain number of enemies to scavenger hunts, to making it to the end without getting damaged or without destroying enemies. Completing challenges gives you a nice selection of unlockable music tracks to listen to, artwork, and character models you can view in the collection room.
At the end of each section you will be faced with a rival battle, a main boss battle, and a special stage. The rival battles are nothing more than simple races that aren't much fun to go through, but the main boss battles are more involved and closely similar to that of their original counterpart. The special stages, which are largely similar to that of the special stages found in Sonic Heroes, have you controlling Modern Sonic in a 3rd person perspective. Under a time limit, Sonic will be boosting down a winding tunnel collecting multi-colored orbs to gain boost and avoiding bombs in order to snag a chaos emerald. Unlike special stages of past Sonic titles, don't expect much of a challenge from these.
The game isn't an absolute technical marvel for the 3DS, but it makes up for it with a vibrant color pallet. The game runs at a very smooth pace and the animations are very fluid. Unfortunately, the 3-D effect is virtually nonexistent, so it's best to leave the 3-D effect off. The sound design is consistently good, featuring a great soundtrack with remixed versions of classic Sonic songs and sound effects that get the job done.
To sum things up:
PROS:
-Colorful graphics
-Great soundtrack
-Fun, fast-paced platforming
-Missions add more to the replay value
-Unlockable music tracks and artwork
CONS:
-Weak story presentation
-Redundant gameplay styles
-Boring rival battles
-Special stages don't provide a challenge
While Sonic Generations is an ultimately more satisfying experience on the consoles and PC, the 3DS version can still provide some fun, fast-paced gameplay. It's a pretty good buy for Sonic fans and a rental for everyone else.