Only counting natural abilities, I consider Sonic better at racing than Dash because of one key factor, endurance! Their top speeds are as far as canon descriptions go similar (both vaguely described as "supersonic" or "breaking the sound barrier"). Sonic however, unlike Dash, has a secondary power of supernatural endurance, whereas Dash has been shown to fatigue quickly at times.
Knuckles wins the strength comparison because... well... he literally punched the "Super" out of "Super Sonic". As much as I love AJ, I don't see her doing anything similar anytime soon.
Tails versus Twilight... well what is there to say about that one? Unlike Tails, who you rarely even see doing anything smart, Twilight show's off that she has a brain and she knows how to use it.
Rarity... "gemstone attraction spell"... enough said...
Cream. Keeping in mind that "cuteness" isn't the same as "kindness" then Fluttershy kind of suffers the same problem as Tails where it's implied that she is the kindest pony in Equestria, but you don't get to see her do an awefull lot of kind stuff, or hear her say a lot of kind things. (Again, keep in mind that "shyness" and "cuteness" are not the same as "kindness")
Oh god... Amy and Pinkie... that's two totally different types of crazy... I'm going to have to go with Amy though, because hers is the "creepy obsessed stalker" kind of crazy, as opposed to Pinkie's "awkward tiring random" kind of crazy.
I'm going to have to disagree with a part of this comment. Tails' intelligence is said to be the only one (in universe) to rival Eggman's. The problem is, like I mentioned before, that he really never does much with his intelligence, so all in all it just feels like it's not present.
Amy rose has a very unrealistic and 1-dimensional vision on reality, she is obsessed with a single individual to the point of folowing him anywhere he goes and has once attempted to beat the crap out of him when he didn't want to come with her. (Also consider the fact that the individual in question has on many occasions told her to piss off.) ---> Ergo, She's "bat-sh*t-insane"!
Pinkie, is hyperactive, she think's in non-obvious ways, and she acts out of the norm at almost all times. She has the type of personality you might call crazy, but really, she does ground herself in reality.