While Sonic 1 isn't bad by any means, I've felt over the past few years that it doesn't hold up nearly as well as the later titles. As far as art goes, a lot of it feels simplistic and flat. The parallax of REV00 doesn't help this. Sonic's walking animation looks fucking terrible with the horizontal alignment all over the place, as well as the lack of an intermediate frame for the head turning. The literal RGB greys and yellows are ugly, I prefer Chaotix's warmer rings and bluer greys. The seams on the lava in Marble Zone are pretty ugly too. Labyrinth's tile background isn't very inspiring to look at, I wish they had kept the cave background of the preview versions. The removal of the animated UFOs in Marble make it feel even simpler. The speed cap makes the game feel sluggish, and it doesn't even make sense to have it because it doesn't apply when not pressing the movement buttons. The on-rails pure platforming levels like Marble and Labyrinth break the flow of the game, don't fit and don't really make use of unique Sonic game mechanics. You could easily have Mario going through those levels. Scrap Brain feels unfinished and underwhelming. I realize that because the later games took what worked and refined it, of course it will pale in comparison. Regardless, is Sonic 1 really worth going back to for the game itself on its own, rather than for completionist or nostalgic purposes? Sonic 2 was a huge step up, and Sonic CD has amazing polish and atmosphere.