Oh man, where to begin. First, hey congratulation on making a series that's gone to 18 episodes, not too many people make it this far. Looking at the reception you've gotten so far, your fans are definitely pleased at where the series is going. Can't say the same, never having watched any of this before. Judging this on it's own merit however, there are many things dragging it down as a movie.
First, man, that writing. I'm really glad you're trying to tell a serious story with loads of characters and sub plots and what not. Nice change of pace from most sprite movies. But man, the writing is so awkward and poorly paced. If you honestly read the script out loud I'm sure you'll realize that no one talks like how these kids are. You keep jumping around from awkward scene to awkward scene like mad and I'm always trying to wonder what the point of what I just saw was. "I'm trying to find my boyfriend." "Isn't that like stalking?" "I have nothing else to do in my life." "Thanks for saving me." "I'm immortal." "???"
If you were trying to establish character motive I suppose you succeeded, in a very quick and slipshod way. People have tendencies of pointing out the obvious, or just plain out saying something that had no bearing on what just happened. The Slime is a great example of him unnecessarily explaining in complete detail what was happening and odd dialogue. And then when people are fighting, holy crap do they talk a lot. Shouldn't they be more focused on beating their opponent than explaining all of their attacks? And I keep trying to take the characters and story seriously, but then they start talking about "trolling" and "playstation games." After awhile, it just got painful trying to get through the movie and then it just suddenly ended on the most random moment to a black screen. No credits or anything, just bam. Done.
So every character is an edit of a Sonic character, that's okay. Atleast you're trying to establish your own characters instead of just straight using a preexisting character. The problem is they all nearly look exactly the same, aside from a few recolours and a scrap of clothing. And there are a lot of characters and aside from a select few, most of them had no distinctive personality, only furthering my difficulty of trying to figure out who is who. We have the shonen action main character, dark brooding guy, whacky impressionable little kid, mysterious magical girl, a cute little mascot, and then a bunch of mooks rounding out the ranks.
Other than that the animation was okay, a little too much negative space for the scenes where there were few characters and more than half the screen was nothing. Could probably just make the dimensions smaller to fix that or zoom in more so there's something on the screen. Nice choice of backgrounds you used, most I've never seen before. The fight scenes worked for the most part, aside from all the talking I mentioned before and how quickly everything happens. Not sure how the boat flipped upside down and the characters outside managed to not fall off however.
Music was an interesting choice, lot of lyrical songs that were really amped up and exciting. Though for the most part the scenes they were used in weren't that exciting. Kept changing a little too much me thinks and with no smooth transition. DBZ sound effects was DBZ sound effects. I guess if you're gonna make a Sonic Sprite movie it's mandatory to use DBZ crap. You used it a little more subtly than most Flashes though.
Well, I'm sure I said enough negative things by now. My man, get someone to proofread your scripts before you start the next episode or just read it out loud. It's obvious you really need to do some more editing on your scripts before you submit a movie, maybe go through a couple of drafts? If you're trying to tell a serious story, it's not gonna work if I don't take the characters seriously.
Keep working at it and I hope you'll make me eat my words someday.