(Note that this is a review for the Wii version of Sonic Unleashed, practically an entirely different game compared to the Xbox/PS3 versions.)
The easiest thing to bash about this game right off the bat is the controls. I played with the Wiimote and Nunchuck setup partly for nostalgia purposes and partly to get the authentic Sonic UnWiished experience, but wow is it painful. It's mostly the Werehog stages that suffer from this control scheme, as you have the Wiimote represent Sonic's right arm and the Nunchuck represent his left, and you have to swing them in different orders to do different combos. But it's so so so finicky, and you'll find yourself just annoyingly spamming one two-handed attack when you don't mean to, making Werehog combat frustrating. Not to mention you have to swing the remote to climb up poles and other such Werehog antics, but those get a pass because I think they're funny. And besides motion controls, for whatever reason, the Werehog is locked to movement in only eight directions, and you lose absolutely all control after leaving the ground for a jump while dashing, two baffling decisions that contribute to the game feeling incredibly unresponsive and frustrating. If these were addressed, maybe I could find the night stages fun. I'm not opposed to the type of gameplay or a slower, more platforming and exploration focused style. It's just a problem because it's, y'know... not good!
Notice how I leaped right into discussing the night stages? Yeah, that's because they make up the vast majority of the game. You'll play ONE day stage (about three minutes long, though admittedly with a couple short and ultimately unsubstantial missions after each one) followed by three to six night stages (about seven minutes long each). I'd groan every time I hit a stretch of night stages and would usually end up replaying some day stages to break up the monotony. It's so frustrating because the day stages are actually decently fun! The game just seems so determined to put the worst part of itself on display.
In the day stages, Sonic's boost works in small chunks rather than a depleting meter as it does in the flagship version of the game or really any other boost game, and this is something I actually kinda like. It creates this risk versus reward element, where boosting will make you go faster, but you won't be able to stop for a bit if you need to. You end up being a lot less willing to boost randomly because of it, and it makes trying to S rank the stages a blast as you need to know all the perfect moments to use your boost. Stages are also littered with all kinds of different paths that make replaying them interesting. My major complaints are that dropping to the ground after a homing attack kills absolutely all of your momentum, and the mapping both jump and boost to the same action causes some control issues. Swinging the Wii remote for a homing attack is satisfying, but comes at the cost of responsiveness (though I never really had problems with it not registering my inputs in that scenario, whereas I definitely had it not register me trying to boost). Again though, the day stages make up a small portion of the game, so they're more like a glimmer of hope in the void than anything.
As for some loose end thoughts, I think the story's good, but I think Chip's voice acting kinda hurts it. I love the idea of a globe-trotting adventure and all the great locations it makes for, and it definitely makes Unleashed unique compared to other Sonic games. And the soundtrack is absolutely phenomenal, using instruments inspired by the areas you explore, being upbeat and energetic by day and more laid back by night (minus the fight theme...).The main theme is perhaps one of the most memorable main themes of any game I've ever played, no doubt helped by its prominence as a motif in other themes throughout the game. Definitely one of my favorite game soundtracks of all time. Graphics-wise, it's fine I guess, though it's hard not to be jealous of the absolutely gorgeous scenery of Unleashed's flagship version. Like seriously, that game is Portal 2 levels of amazing and feels like it hasn't aged a day (based on footage I've seen, at least). But yeah. My verdict is that Wii Unleashed is a game that has moments of amazing potential awash in a sea of frustrating mediocrity.