Sonic 4 is the game that is supposed to take Sonic back to when it was good.
The art styIe is very similar to the older Sonic games, though updated of course. Some boss fights are very familiar and so are the tunes. That said, Sonic 4 have some new concept making it feel quite fresh and throughout most of the first episode the game delivers a lot of fun. Also, it is nice to be able to save the game when you complete a level, at least for those of us who aren't that interested in getting a good score on the game.
Most of my complaints about the game are the same as what I disliked about Sonic the Hedgehog 1. The most obvious is that Sonic just moves too fast. This is a paradox because moving fast is also the most enjoyable part of Sonic. The only problem is that when you move so fast, you will at one point jump into a pit, hit an enemy or simply a wall, for the anticlimactic feeling of needing to slow down for a moment.
Another thing I don't like is the controls, though it just becomes a problem a few times in the game. More specifically, if you don't have that much speed before a jump, then the moment you let go of the directional button, you will fall straight down, which is a bit of a pain. One of the hardest parts of the game, which really should have been the easiest, was when I was on a small platform and had to jump to another platform nearby. Sonic accelerates really slow. Which is strange for someone with his capacity of maximum speed, and that made the controls so awkward I missed the platform over and over again.
There are some levels that requires you to be underwater as well, which is even worse in Sonic games than it is in other 2D games.
The final boss is also frustrating. Not necessarily because of the difficulty, but because moves that should work doesn't. The start is very simple, but takes some time, and the boss changes moves often, so having to use trial and error every time he changes his moves makes it take much longer than a boss that is actually not that hard should. Also, considering you run out of lives, it take even longer.
Most of those complains are small, but then again it is a short game. It lasts about 3 hours and costs 1500 Wii Points. The game no doubt has its ups and downs, from levels that are fun, fast-paced and sometimes stressful in a good way to levels that just makes me angry with the level designer. It is a good game, but for a relatively high price I will not be getting the other episodes.