Some people may find this Sonic game very weird, and will not like it. I for one really loved this game. It's just as good as classics such as Sonic 1 and Sonic 2. Many Sonic games have okay storyline, but suprisingly, this has a very good one and used the time travelling plot and even managed to stay true to Sonic 1. The music is excellent and the level designs are even better. The Robotnik bosses are extremely original, especially the one with all the bubbles as well Also, this game marks the first appearance of Metal Sonic and Amy Rose, and I am a big Metal Sonic fan so that was a good thing. The rivalry was great and I loved the fact that Sonic actually had a bit of competition and wasn't the only fast character. It made the franchise a lot more entertaining, to be honest. This game will last quite a bit of time too since they are time trials, and they are pretty fun. The graphics were like Sonic 1 and I think the Sonic design they used in that game were the best. This is a lot better than some of the later Sonic titles and even some of the 2D ones as well.
Looking back on it, it doesn't really look that aged. If you want to see Sonic at his finest, then play this game. It's definitely worth it!