There's been a lot of talk about Sonic 4 just cashing in on the trend in nostalgia gaming. Of course it is. That's pretty obvious, but in many ways Sonic games needed to take a step back anyway. The only truly great mainline Sonic games in the last decade were portable 2D platformers developed by DIMPS. In contrast, the only great Sonic game Sonic Team has developed recently was Sonic Adventure, 11 years ago.
But in many ways, Sonic 4 was too many steps back. The Sonic Advance and Sonic Rush games returned the series to its roots while also bringing some much needed innovation. Sonic Rush in particular is now one of my favorite games because of the addition of boosting and the boost gauge. Sonic 4, though, keeps only on of the innovations from the latest 2D Sonic games, and that's the homing dash. But enough rambling, let's break this game down category-style.
The music of Sonic 4 is deliberately nostalgic, and painfully so. Although the game was composed by Jun Senoue, it's far from his best work. Anyone who has played recent Sonic games knows that Jun Senoue's best work is when he's free from stylistic limitations. If he's free to use whatever instruments he pleases, we get excellent synth-rock tunes to enjoy for hours. However, when he's limited to Genesis synth samples, well, we get something that sounds like Sonic 3 and Knuckles, only less catchy. The game does have a few tunes that I'll be humming in the future, and none of the songs are outright bad, but they aren't great either.
The Sonic Advance games are beautiful. Gorgeous pixel art with a ridiculous number of frames of animation. Sonic Rush less so, having replaced lots of sprites with cel-shaded 3D models, but still rather pleasing, with nice levels and backgrounds. Sonic 4 isn't bad-looking, but it's rather..plastic. Everything in the game looks like mid-90s prerendered CG. Lots of bright colors, and very well-animated, but no style. Meh at best.
The designers of this game have never heard of the conservation of momentum. The physics are just plain weird. Releasing the d-pad at any time feels like some sort of punishment, because you will come to a halt immediately, even in mid-air. Every platformer has some amount of mid-air direction change, but this is ridiculous. Add to that some weirdly inconsistent homing mechanics. Heaven forbid you go a pixel past the center of the object, because you'll dash forward instead of at the object that still has a homing target painted on it. And then there's Sonic's ridiculously slow acceleration; something that had been completely fixed in Sonic Rush.
The level design is top-notch, exactly what I expected from DIMPS. It has a rather Sonic Advance 2 feel to it, with lots of areas to run around like crazy and lots of platforming to be done. Thankfully the random fun-breaking mini-boss fights from Sonic Rush are gone. The level themes, though, are again too much on the side of nostalgia. It's like they took the most iconic zones from Sonic 1 and 2 (Green Hill, Casino Night, Labyrinth, Metropolis, and Death Egg) and reworked them. Although the layouts are more or less new, there just wasn't a trace of originality in any of them.
The boss-fights are frequently complained-about, but I can't understand why. They're quite solid and familiar with new twists. Generally they're divided into two phases; one ripped straight from a Genesis game and one completely new. The completely new phases are good fun, and there is even a running boss, which DIMPS does so well.
Left to do is get all the Chaos Emeralds. I'll probably add some comments when I do that.
Despite all my complaining, Sonic 4 is a really solid game. It's easily the best Sonic console release (discounting ports) since 1999. The worst thing about the game is that while DIMPS Sonic games have consistently taken at least one step forward, Sonic 4 feels like two steps forward, one step back. The physics needs a major overhaul, and they need to tone down the nostalgia. Really, I get the feeling that if DIMPS had been left to their own devices, we would have gotten something just as amazing as Sonic Advance 2 or Sonic Rush. As it is, I see a heck of a lot of wasted potential.
Still, I give the game 8/10. If you loved the Genesis games and missed out on the Sonic Advance/Rush series, you'll have the time of your life. Otherwise, you'd be better off replaying Sonic's DIMPS-developed portable adventures.