These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Even Better Sequel: Rivals 2. More playable characters, better level design, better graphics, better soundtrack, and to top it all off, a Free Play mode where you can just run through the level by yourself with no Rival. While this is unlockable, it's a godsend to those who just want a classic Sonic experience with straight platforming and running.
So Okay, It's Average: By and large, those who have played the Rivals games don't see anything particularly bad about the games, but also nothing particularly good that stands out.