40% Awesome, 60% Mediocre
First off, the story. If you're expecting an epic and memorable plot, well, look somewhere else. Sonic Unleashed's plot is deeper than Mario Galaxy's, though that isn't saying much. Eggman has broken the world into multiple pieces and you as Sonic must bring them back together. This time, you're aided by Chip, who is destined to become Sonic's Navi. What I mean by that is annoying. But, unlike Navi, Chip isn't helpful. The cutscenes are well-done, but for whatever reason you can't skip them. This poses a problem specifically because of the "meh" voice acting and Chip. Then again, the franchise has never been known for Hollywood grade voice acting, so I'm sure plenty of people saw this coming.
Next, the gameplay. It's broken up into two main sections: the fast and enjoyable daytime stages and the somewhat mediocre nighttime stages. Onto the daytime stages. They're fast-paced, well-designed, and just plain fun. Rarely, if ever, do you die from a cheaply placed deathtrap. There are also plenty of shortcuts and alternate routes to encourage replaying the level. While this does give the game a great sense of speed, it does make it easier than expected. There are also challenge levels like "Collect x amount of rings" or "Beat it within a time limit", but they don't add that much replay value. Like the Sonic Rush games, you have a "Boost Gauge", which allows you to pull off quick speed boosts, as it's name suggests. You refill this gauge by taking out enemies and collecting rings. However, in more confined sections of a level, the boost does you more damage than good. The controls are simple (A to Jump, B to Drift, Z to Crouch, Analog stick to move, etc), but my only complaint is shaking the Wii remote to pull off a dash or homing attack. It is responsive, but just feels awkward and out of place. Here's an instance where a simple button press would suffice. If you don't like the Wiimote and Nunchuk setup, there's the option to use a GameCube or Classic controller.
Now for the nighttime stages. "ZOMG! The Werehog beat em up stages are really repetitive!". This doesn't strike me as a bad thing seeing as ALL beat em up games are repetitive. Final Fight, Devil May Cry, Streets of Rage, etc. All of these boil down to "Beat down a group of enemies, progress, beat down another group of enemies, progress more" rinse and repeat. One of the problems with these is the controls. Platforming here is fairly awkward and the running is somewhat pointless, given how many bottomless pits there are and how easy it is to accidentally run off a platform. The motion controls here are kind of awkward. Swing the nunchuk to throw a left punch, swing the Wiimote to throw a right punch, etc. For these sections I recommend using the GameCube controller. You can also buy new combos, moves, as well as upgrade your health. But ultimately, the nighttime stages are fairly generic and somewhat shallow. It's just disappointing that there are more nighttime stages than daytime stages.
The game looks great from both a technical and artistic perspective. The graphics are great...for a Wii game. Sorry I had to end the sentence with that. Anyway, the game contains plenty of nice graphical effects like particle effects and so on. The bright and colorful art design (even during the nighttime stages) is also a nice break from the countless beige, brown, and gray colored games of this generation. As for the soundtrack, it's a big improvement from previous Sonic games. Fantastic orchestrated music replaces the typical electric guitar music that has (kind of) become traditional for the series.
So in the end, Sonic Unleashed feels like a missed opportunity. While the impressive presentation, graphics, soundtrack, daytime stages, and large amount of unlockables merit is as a good game, the Werehog stages and tacked-on motion controls hold it back from being a game everyone must play. It makes you wonder...will Sega ever gives us a 3D Sonic game without any mediocre gimmicks? Perhaps, one day.