Too much Gimmick, Not enough Gameplay
Basic story behind unleashed(which is the same for both versions) is that Dr. Eggman has discovered the "Gaia Manuscripts" which detail some horrible monster slumbering within the earth's core which he plans to release to help him conquer the world(totally original). Before setting his motions in plan Sonic arrives and with the 7 chaos emeralds manages to carve a passage of destruction among his ginormous fleet and corners him in what either must be a private installation or a redesigned space colony Ark. Eggman pleads with sonic for forgiveness, betrays him within the next 8 seconds and drains the energy out of the chaos emeralds, which brings in the werehog and launches him and the emeralds out into space hurling through the emeralds atmosphere. Sonic survives the crash and meets up with Chip(important later), who has lost his memory and convinces Sonic to help him get his memory back(guilt routine by sonic).
Unlike the HD twins, the hub world here is simple: You point and click to move from one place to the other. Important sites will pop up after you cycle enough times through and eventually you will get to the actual non level part of the game...The Gaia temples. Basically all you do in here is run over to the Sun or moon path(depending on what the game decides) and move on towards the level.
The levels in sonic unleashed Wii are decently long your first playthrough, but not long enough to drag the game, so in order to solve this, MANY other side missions of sort were added, making their return from Secret Rings. Sonic's gameplay within these levels are for the most part the same as the HD version, barring the boost which is not continuous, and level design which is more awkwardly wide. Unlike the HD version, and probably one of the better decisions, was to have Sun and Moon medals awarded based on rank rather than hide and go seek, making the game that much simpler.
This wouldn't be such a disappointing title if the Werehog didn't take 2/3 of the game. That's right, for every one daylight, sonic boosting level you play, there are about 3 levels of nothing but werehog, and that's just the main missions not counting the side missions. Because of his speed, these sections tend to drag on forever and serve as the platforming sections of the game(though why they just couldn't get sonic himself remains a mystery). Mass amounts of Waggle combat and stick thrusting to run only implore the length of these levels, some of the having rather poor enemy placement or design such as one of the Adabat night levels.
Eggmanland, making it's rather first appearance is the final level of the game in which of course you fight your way in to defeat the old doctor himself. The wii version, while still requiring a large amount of precision to complete for even a decent rank, is much more forgiving that it's HD counterpart and even managed to separate the werehog and sonic levels to make it easier.
The Egg Dragoon is largely unchanged from each version. 1st phase of the Final boss is a giant QTE, nothing too bad, and the second phase is simply mashing the quick step button to avoid attacks and homing attack when indicated.
Overall, the mass attention to the werehog given here pars the game on with it's HD counterpart, which had a 1:1 ration on levels. It becomes moderately fun when completed and even to challenge yourself a few times with the day missions, but too much on the new aspect and nada on the old leaves a sour taste on what could've been a great sonic game.