Not helping is that the halfpipe structure was overused in several Sonic games before it. Episode II's Special Stages recycle the halfpipe structure from Sonic 2, and are incredibly difficult, especially the seventh Special Stage. Episode I has easy Special Stages that are really tedious and are recycled from Sonic 1.

The episodic format not only makes the development more complicated, but it's also a pointless addition, not to mention that plans for a third episode have so far been abandoned.

Before the final boss, like in Sonic Advance 2, you must fight all of these bosses again in a tedious boss rush.

Episode I has nothing but the bosses from the older titles but with pinch modes!.

(Green Hill being Splash Hill, and Sky Chase being Sky Fortress)

This game started SEGA's terrible habit of nostalgia pandering: Both episodes reuse level themes and parts of their names from the Genesis titles, which is extremely lazy and unoriginal.

The Homing Attack is pointless since the only reason why it was added in the 3D games (starting with Sonic Adventure) was that defeating enemies by jumping into them was much harder in a 3D space, yet this game is in 2D, so there's no point.

Barely any hidden areas or secrets, the level design just consists of autopilot sections, linear straightforward pathways, and dull platforming with constant use of Homing Attack chains, just like recent games of the series.

Due to some unusual choices for the synths in the soundtrack, it is commonly said that some songs in it 'sound like cats' and that Act 2 of Oil Desert Zone 'sounds like dying ducks'.

They have a Genesis-style sound to them, especially with the pistol-like drums, which doesn't sound great for the most part.

Despite being composed by longtime Sonic composer Jun Senoue, the music doesn't sound as good as Sonic 1, 2, CD(both the American and Japanese soundtracks), or 3 & Knuckles.

The worst part is that the game sometimes plays itself, with lots of speed boosters and springs everywhere for no reason, even when it's something as basic as running to the right.

The physics are very bad, since you can get stuck on walls a-la Spiderman, you completely lose momentum when jumping after a Spindash and you only get slower when you roll into a ball, even when going downhill, this is due to the fact it uses the Sonic Rush engine, which is not capable of non-boost gameplay.

Sonic 4 episode 2 final boss