Sonic the Hedgehog 4: Episode I is designed to recreate the classic platforming action of Sonic 1-3 much the same way Mega Man 9 and 10 did for Capcom's famous series. Sonic 4 comes close to accomplishing that objective, but its new graphics and basic gameplay mechanics falter. Most gamers will, immediately upon opening the game, ask two questions: "Why is Sonic slow?" and "Why give a classic-style Sonic game 3-D graphics?" After they've dealt with those issues, there's a decent game here, if perhaps a bit disappointing.
Sonic's physics immediately feel wrong. It doesn't break the game or even make it worse, it's just... different. Players pick up the controller, press right on the D-Pad to get going, and notice that Sonic chugs a bit before he gets running at any reasonable speed, and it just feels bad. As soon as you're used to it, it's only a minor annoyance, but nowhere near the franchise authenticity that Mega Man 9 and 10 brought in terms of classic game physics.
Speaking of a feeling of authenticity, the new 3-D graphics are incredibly pointless. The old Sonic graphics carry nostalgia and look perfectly fine, whereas the new graphics try and fail to copy that art style, and it looks unsatisfying throughout the game. Again, just a minor annoyance, but the 3-D graphics add nothing to the game and don't actually look any better than the SEGA Genesis once did, they just look a bit more current.
But once gamers have gotten past those issues, there's an okay Sonic game here. The level design is ripped straight from the old titles so clearly that you can call out "Oh, this part's just like Sonic 2!" for several sections of the game, but it's still fresh enough to present a challenge and keep interesting for each level.
The difficulty level is extraordinarily easy, except for a few points of near controller-tossing frustration, like one boss fight full of insta-kill pillars that will likely eat up a lot of the life-ups you've collected through the game to that point. Several enemies pop up out of nowhere as you're speeding along, giving you no warning time to successfully dodge them and actually, you know, feel cool like a Sonic game should, but you can still always collect your rings and move on. Life-ups are pretty plentiful and deaths are somewhat scarce, so the game moves pretty quickly and is not very difficult to beat.