I get that the game is really old, but it does feel really clunky. That said, for a game originally released in 1998, it's still really good. The first time I played this was back in 2018, and the younger me couldn't appreciate older media back then, but playing it now I can see how much better it was and why people praise the Adventure games. I like the formula a lot, my only issue is the other playable characters. While Sonic is really fun to play, the other characters can be a hit or miss. Tails doesn't add much from Sonic, Knuckles hunts for emerald shards but that can either be fun or annoying, Amy runs from a robot and her levels are slow and tedious, Big is just awful, and Gamma's run and gun type gameplay is pretty good. If I had to rank each story, I'd say:
1. Sonic
2. Super Sonic
3. Gamma
4. Tails
5. Knuckles
6. Amy
7. Big
Even though some of the characters aren't that fun, I do like seeing certain events happening from the other characters' perspectives. Not only that, but a lot of the other character stories are pretty short. Big's story is awful gameplay wise, but the story itself is extremely short especially without counting the cutscenes. Speaking of the cutscenes, the animations and voice acting sometimes feel really stiff. Tails is a good example of this; his voice feels almost too awkward for my liking. Though some of the other voices like Sonic and Eggman work very well for their characterization in this game. Honestly the only things holding me back from giving it 5 stars enjoyment wise are how old the game is. I said earlier I can appreciate older media but the game is still very clunky at times and I feel like a modern remake of the game would do it justice. That being said, the game is still fine as it is now, but it's not perfect. Overall, I really enjoyed this game despite all the flaws and I'm glad I can appreciate it more than I did when I was younger.