:V does have a good point.
It's not bad losing to Knuckles. Knuckles, next to Sonic and Shadow, is like, one of the best characters in the series. Canonly and speed-wise, he's almost as fast as Sonic and Shadow are, and on top of that (with possible exceptions of Mighty or Omega) is one of the most powerful characters.
...
Man. Knuckles would have been a high/top tier beast if he were in Brawl.
[EDIT]
Also, it's come to my attention that as of late, they've been changing the strengths and capabilities of a Super Form. To me, it's no longer about being invincible anymore. In Sonic 2006, Solaris was capable of knocking rings out of the three hedgehogs, and in turn, that counts for damaging them. And in Sonic Unleashed, the 360/PS3 version, Super Sonic had a health bar instead, signifying that he could actually be damaged and killed.
I believe that Super Sonic is just so immensely powerful, that unless you are beyond godly in strength, you won't be doing much more than pushing him away; it gives the idea that he is invincible when he really isn't. Everyone else is just pathetically weak in comparison to his super form. So in essence, and I hate to bring up the DBZ comparison, but the super forms have become something akin to the Super Saiyans. If you're not strong enough, they WILL come off as invincible. But match their power and then some? You will hurt them.
[EDIT #2]
Sorry, by canon I'm talking video games. In Sonic Adventure 2 (if you hack to play as him on Sonic and Shadow stages, his top speed rivals Sonic and Shadow), the older games, the Sonic Advance series, Knuckles is really fast. And I personally think Knuckles would be pretty dang good. Good speed AND sickening strength? The speed that Ike wished he had but it's with Knuckles. That's my thing there.