Late response.... Years ago back at the Sega Forums, there was an Automation topic concerning Sonic 4 where at one point, someone dug up and posted some old reviews for Sonic 3 and Sonic & Knuckles (in particular, Hyper's S3 review and Megazone's S&K review) and people were drawing similar conclusions--reviewers getting tired of the franchise by that point, despite the series being only three years old. I think the problem there was that S&K was being pushed as a traditional new Sonic game; despite the game itself essentially being little beyond a Sonic 3 level expansion pack. Obviously we know the real answer in that they were one game split into two halves, but you wouldn't conclusively know from either the marketing or the game's presentation. Sonic 3's ending is conclusive enough that you wouldn't know that the story doesn't actually end there if you didn't have Sonic & Knuckles, and Sonic & Knuckles (in-game) likewise doesn't bill itself as a direct continuation of Sonic 3's story beyond the title screen. And while the lock-on technology was heavily promoted in S&K's advertising, it was presented as more of a bonus element (Play as Knuckles in Sonic 2 and in Sonic 3!) instead of being the essential way to play both games (Play Sonic 3 and Sonic & Knuckles together as one interconnected story/as one big adventure!). This especially hurts S&K's standing given that Sonic 3 was only released six months prior, so you could easily see how "fresh" Sonic & Knuckles actually was in comparison. I feel the reception for both games (since even Sonic 3 in some reviews had some of these 'more of the same' responses S&K was hit with, no doubt to it being rushed) would had gone over better if Sega was more willing to admit and market them as two episodes of one project, or at least pushed S&K further back and refined it to make it more standalone/more evolved as a game from Sonic 3. (Or somehow, against the odds of the McDonalds' Happy Meal deadline/cartridge production costs/otherwise hectic production cycle, was able to release everything as one singular "Sonic 3," and avoid this whole mess.). But that's veering into "what could have been" territory.