Wow...
First off, this was dull, pointless, and poorly animated. Not only were the "fight scenes" (if you could even call them that) boring, they were dumb also. I don't seem to recall "good 'ol Sonic" ever enduring an enemy attack, especially one of the magnitude shown in the Flash, without a scratch. That didn't fit in with the retro feel at all. Also, I'm pretty sure that planes aren't capable of space travel or that Sonic, Tales, and Amy could survive in space without freezing or needing a little thing called oxygen. Also, while I'm talking about factual errors, I couldn't help but notice that Earth was somehow able to maintain a strong and constrant gravitational pull on Amy when she was released from her captive. Even if I was to accept this, it would also be hard to accept her flawless, and animationless, landing after falling several miles through Earth's atmosphere without burning up on entry.
So... I didn't like the animation.
Also, while I'm still in a bad mood, Sonic CD came out in 1993 while Sonic the Hedgehog 2 came out in 1992. If my basic math is correct (and it is), that means that Sonic 2 came out first. Also, Metal Sonic first appeared in Sonic CD, not Sonic the Hedgehog 3.
So... overall, bad "animation" and the "artist" knows nothing about sonic, as indicated in both the animation and comments.