Sonic 2 overall does a great job at defining the series and improves on its predecessor in pretty much every way. Most importantly, the level design is vastly improved to be more focused around speed and physics, combined with the newly added Spin Dash that makes the levels a lot more fun to play. However, the quality starts to drop off starting with Mystic Cave, with the levels feeling a bit more unfair in terms of getting hit or dying by things you couldn't see coming. Despite that, I'd still say that Sonic 2's lows are still higher than Sonic 1's lows. The bosses are alright though the second phase of the final boss can feel a bit janky and take a while. The special stages are solid enough minus Tails running into spikes from time to time. In conclusion, Sonic 2 does everything a sequel should do to the point that it's easily worth playing more over the original. (Played via the Sonic 2 Absolute version on PC)