Just a few more comments about Generations, perhaps a mini review of sorts:
When I first watched some of the previews of Modern Sonic before the game came out, I thought to myself, "I wish there was more exploration". After playing a bit, I almost feel overwhelmed by the amount of exploration in the later levels, and that's a good thing. I'm actually having a whole lot of fun just searching through all the later levels. In terms of how the levels are structured, it feels like the exploration is more linear/restricted than SRB2, but at the same time, it doesn't negatively affect the game at all. I was honestly extremely and surprisingly pleased with Modern gameplay.
As for Classic Sonic, I've been playing Classic a bit more and although it's quite a bit different than the originals it's becoming more fun for me. At first I was really disappointed with the physics - bouncing off enemies sends you a predetermined height, awkward jump when moving slow, vertical springs cancelling all horizontal momentum - but after playing more, it's not bothering me nearly as much. Most likely the biggest reason for these physics was to make it more simple and reasonable to reach alternate paths using enemies as the means of which to get there. I still wish that the physics were more like the originals, but I also believe that this version undoubtedly has its own merits.
Overall, I'm extremely satisfied with Generations and will be playing it for quite a bit longer. Even though I've played 30 hours so far (way too unproductive), I haven't beaten the game or even reached halfway with the achievements. Having too much fun exploring/speedrunning. Even if I get bored of the game sometime soon, I know I'll definitely be replaying it in the future.