WesternAnimation The Premise was Promising, but the Outcome was Disappointing
I remember when I first heard news of a new Sonic the Hedgehog animated series, what would eventually become Sonic Underground. I had thoroughly enjoyed the Sonic the Hedgehog Saturday morning cartoon when I was about five years old, and being older, I was interested in the new show from what little information I could find: The idea of Sonic and his siblings navigating a new rustic and cyberpunk-inspired Mobius while fighting Robotnik sounded like my ideal television adaptation of Sonic. It's only been recently, however, that I've been able to watch many episodes of the show. From what I've watched, I can say that my high expectations of the show have not been met.
The very worst thing about the show, of course, are the songs that Sonic, Sonia, and Manic are obligated to spew forth once an episode. Aside from being horrible to listen for the most part in spite of the efforts of the vocal cast, the songs eat up a good two to three minutes that could be better put to use further developing the roughly-twenty-three minute-long stories. The songs also serve as a tired Deus ex Machina, which may look and sound sort of cool the first time but not the first twenty times.
The show suffers from another tedious plot device, whose name is Sonic the Hedgehog. If the siblings' instruments of destruction fail to save the day, Sonic's ridiculous speed will, to the point that Robotnik doesn't even have time to push a button for his plans to succeed. While the same issue affected Sonic Sat AM to a lesser extent, it was at least balanced out by the other character's own visually-appealing skills, like Bunnie's strength or Sally's technical prowess. By comparison, Manic's sometimes-ability to pickpocket is usually visually unengaging, and Sonia has very few redeeming qualities to counter how many times she complains about sewers, dirt, etc. Furthermore, whenever Sonic runs, he's usually reduced to a boring neon-blue smear.
That isn't to say the show doesn't have some strengths: The character designs, if not good, are at least interesting for most non-hedgehog characters. Sleet and Dingo are reasonably entertaining expies of Scratch and Grounder. There are also a few episodes (namely "Three Hedgehogs and a Baby", "Six is a Crowd", and the Chaos Emerald arc) that approach Sat AM-quality. But these don't rescue generally-weak storytelling.
WesternAnimation Sonicmaniacs
You know, I don't find the show bad at all. It's OK.
The premise is quite interesting: triplets Sonic, Sonia and Manic are separated shortly after they're born by their mother, Queen Aleena, and adopted by other people for their safety to be hidden, then the triplets reunite when they grow up a bit, then when the right time comes, the triplets will reunite with their mother to form the Council of Four to stop Dr. Robotnik once and for all. Too bad it didn't reach its conclusion, even after comics were planned to finish the story.
Okay, I find the songs catchy. There, I said it! Please, don't harm me! Kiddin' (somewhat)!
Well, Sleet and Dingo were the most entertaining characters here, because Maurice LaMarche and Peter Wilds are fully commited to their jobs. And they never dissapointed me. Gary Chalk was fine to me as Robotnik, but I missed the hamminess of Long John Baldry or the menacing presence of Jim Cummings... and Jaleel White does his final ode as Sonic the Hedgehog (not really) and pulls triple duty as Sonic, Sonia and Manic (they were quite interesting). And I was fine with him as Sonia.
In other words: the show was quite good and interesting, but it never reached its potential at its fullest or its conclusion.