Which Comes First, Sonic the Hedgehog 2 or Sonic CD?

gamerant.com:

Recent announcements for Sonic the Hedgehog tend to be pointing toward a shift in Sega's most famous brand. Sonic Origins sees the first four Sonic games remastered and enhanced for a new generation, with cutscenes added to tie them together. Fans have noticed that Sonic Origins lists Sonic CD between Sonic 1 and Sonic 2. For many years, where Sonic CD falls in the timeline has been a big debate among fans, and now Origins has shined new light onto the discussion.

It's understandable why Sonic fans have questioned where Sonic CD fits into the timeline, as it sits in an awkward position aesthetically, as well as in terms of its development. Sonic 2 and Sonic CD were developed at the same time, with the general idea behind Sonic CD being "Sonic on the Sega CD" rather than being a direct sequel, according to Naoto Ohshima. Ohshima is the director of Sonic CD, and has mentioned that the fact CD wasn't a numbered title changed how Sega treated it during development compared to Sonic 2, which released first. The way the development of these titles differed puts them both in unique spots, but this hasn't helped with the question about which comes first.

Why Sonic Origins' Approach to Amy is Problematic

In Sonic the Hedgehog, players can only get the true ending if they manage to collect all the Chaos Emeralds from Special Stages. The same secret ending applies to Sonic 2, and the sequel also introduces Super Sonic as a reward for completion. With how Sonic CD focused on the Time Stones rather than the Chaos Emeralds, some fans feel it makes no sense for Dr. Robotnik to drop the endeavor of finding the Chaos Emeralds between adventures for different gemstones altogether. Sonic the Hedgehog 4 also made a case that CD happened after