Someone's gotta say it...
First off, nice sprite animation, you did good on this. I'm a fan of sprites, and this one, animation wise, I really enjoyed, even though I haven't seen the first one. But there's a reason I'm giving you a 3/5 and 6/10, and that reason is; Voice acting.
Usually, sprites aren't voiced (not saying that's a bad thing that you did it, just saying), and it's interesting that you chose to use VA's for this series. But the voices themselves, I'm not impressed. Mostly Sonic, Nero, and a little bit with Eggman. First (just some recording advice), use good quality sound recording equipment; you can hear that weird sound you get when you're too far away from the mic, like they're in a big open room, and it just sounds tacky. But anyways, back to the voices.
Most of you guys did really well, but the ones I mentioned before, you guys just didn't seem that "into it". It really sounded to me like you were doing a halfassedou job, and you can't do that when you're working on this big a project. Nero was the biggest problem of all. Worm, please don't take this personally, but you really sounded like you've got a speech impediment or something going on. Next time try to take it more seriously, because it didn't sound like you were giving a full hearted performance. When recording, go over it multiple times, take your time and talk as clearly as you can, and put more emotion into it. And the same goes for Sonicking, you could use the same advice.
And as for Eggman, I don't know if it was a recording issue or just an editing thing, but the voice, as good as it was (actually one of the voices I enjoyed), it sounded very mechanical, like someone put it through the filter used for the metallix voices. It was a convincing voice, but try not putting it through the filters (or just use better recording equipment).
Now, the general dialogue could have been better as well; the timing was just either too fast or too slow in a few places, so making a more fluid transition between each piece of dialogue will really help make this more convincing.
So I guess that's it. Not being a spriter there isn't much advice I can give you on animating, other than work on timing more, maybe even take some notes from Alvin Earthworm. Please take into consideration what I have to say next time around, because you've got a really good story, and it would be a shame for it to be ruined by bad voice acting (personally, with sprites I don't really see a need for voices, but whatever, it's your thing, make it great how you want it, people will like it when it's at its best). I am sorry I gave you such a low score for this, but I do wish all of you on the team the best of luck on the next episode, I'll be sure to keep an eye out for it in the portal. And always keep improving. :) Peace.
(unimportant side note: longest review I've ever written XD)