Sonic X is basically what got me into Sonic The Hedgehog in the first place and is the best Sonic cartoon ever (and also the most accurate to their in game counter parts). Season one is a bit boring consisting of episodes that feel like filler. Season 2 is the best season. It follows the storylines of Sonic Adventure 1, Sonic Adventure 2, and a little bit of Sonic Battle. The story is so good. It draws you in, making you want to see more. The arc that fallows SA2 in partular is exstreemly good. The story of the ark, Shadow, and Maria, is the vary reason I became a Sonic fan. Season 3 is the worst season of Sonic X (in my opinion). It takes place in space so it's hard to tell how much time/distance has passed since the last episode. While the story of the Metarex is interesting, the Metarex themselves are kinda one-note. Cosmo is the best part of the season. Her story and growth throughout the season make season three more bearable. Pretty much all Team Chaotix episodes are extremely funny and entertaining to watch.
The characters in Sonic X are really good and the most accurate you will get to the game depictions of the charaters (as of 2021). Sonic and his friends have so much personality and depth that I can't help but be invested. Characters like Shadow in particular go far beyond pure evil or pure good. These are the kind of charaters that could be doing any mundain task and it still be intertaining.
However, Chris Thorndike (who is basically the protagonist of the show) is just the worst. I did not mind him in season 1 and most of season 2, but the season 2 finale is so bad that it retroactively ruins the character, making season 3 nearly unbearable. Aside from Chris, all the charters are exstreemly like-able.
Overall I would say this, Sonic X is the best Sonic Cartoon ever. Though it is not perfect, the story of season 2 and the characterization more than makeup for its shortcomings. If you are a Shadow fan (like me) then I highly recommend watching this show. If you don't know anything about Sonic, then I would also recomend this show, it's a great introductray for the seres and it has alot to offer exsisting fans. Also, it has a good amount of rewatchablity.