I may still enjoy playing this game but I just can't look past how bad it it from a modern perspective.
In the past, this game easily met my expectations but time hasn't been kind to this game. With quite a few flaws peeking through the rough exterior. Other than the characters the story doesn't have anything to do with the first game with it starting with Sonic escaping a city full of robots. Or with Eggman, as he releases the ultimate lifeform Shadow from an island prison. The dual story idea was a cool idea that Sega never really managed to do well again. Depending on which side you choose the story changes slightly with them both being interconnected it mainly just allows for some exposition that you wouldn't see otherwise.
It may be split between light and dark but they both have 3 gameplay styles. Sonic/Shadow are all about going through a linear level quickly. They can take out enemies with a homing attack and light speed dash through rings. Tails/Eggman have a mech that can lock onto enemies and fire missiles/bullets at them. Out of the three gameplay styles, this one has the longest stages that go on for a bit too long. Finally Knuckles/Rouge get to fly around a level to find hidden pieces of the master emerald. None of the levels are huge so it never took me that long to find all the pieces. This game constantly swaps between each of these 3 characters so it never really gives the player a chance to get good at a certain style of gameplay. At the same time, it does give the game plenty of variety too.
I couldn't bring up an SA game without bringing up Chao's. Since they are the pet raising the mini game of this franchise. Enemies in each of the levels can drop animals or energy lights that can raise a Chao's stats. After raising them enough they can then be thrown into a race or fight. If they win you will obtain a Sonic Emblem. At least for me the emblems never seemed worth the effort it took to collect them since they only unlocked something after finding all of them. This game also includes a Kart racer and a vs mode. Both aren't really something I can play right now and from the single player, the Karts don't control that well anyway.
In general, all of this is well made with each level being made for the abilities you have access to. Yet a lot of things started to pop up. Like the fact that every cutscene doesn't have a good sound balance. So most of the time you'll be hearing a rocking guitar solo over the voice over. Sure the plot isn't some amazing story but it would be nice to hear what they are saying instead of reading the subtitles. With most of the bosses being vs another playable character they mostly just seem easy with the few unique ones standing from the rest. Even some of the levels don't seem balanced that well with me falling to my death a few times because of the lack of accurate auto aim on the homing attack. As mentioned before some of the levels also overstay their welcome. Especially the last stage that caused me to have to replay it after losing all my lives.
Still, overall the game is alright. I think the Gamecube version actually fixed a few of my issues. But that isn't what I'm playing now. So it is really hard to recommend this game to anyone. As a whole, I may still like it but at the same time, I see all the flaws that contribute to it being a less that perfect game. If you can look past the flaws like me maybe it is worth revisiting this adventure one more time. Otherwise, it might be best to just stay away.