What? No, this is incorrect.40:60's are completely winnable by being slightly better than your opponent. Having nothing worse than 40:60's with top tier opponents would mean there would be more Mario "champions", like with Sonic, Ike or Yoshi. I'm not even saying those characters don't have matchups worse than 40:60 because I'm pretty sure they do. Yet they can place decent, something Marios haven't really been able to do.
The emergence of "champions", as you call them, amongst mains of a particular character has more to do with the skill of the players that chose to main those characters. If M2K decided that he were to main Mario, he'd do well (not as well as he does now, but he'd make a splash) and be considered a "champion". Characters having players that do well with those characters has more to do with luck (of them playing said characters) and the number of mains there are than their match-ups. That would explain why the number of "champions" per character varies so much. Pit doesn't really have ANY does he? DK has like four or five...three of which live in the same state (used to be four). They're both very close on the tier list, and I believe Pit has overall better match-ups.
That said, you don't consider Boss a "champion"? His placements with Mario have always been notable...although most are at locals.
This is not always accurate. There are some who perform well above what's expected in regards of these ratios and there are some who perform well below. That doesn't always indicate variance in skill but sometimes in playstyle, match-up knowledge, or sometimes it's just incorrect. There are far too many variables for this standard to adequately cover every match-up.Having a 40:60 means you're expected to win at least one set out of every three against an opponent of the same skill. 30:70 means at least one out of every 4 sets.
I've always taken 45:55 to represent slight disadvantage, but still winnable. Just slightly tipped in the opposition's favor.
40:60 represents moderate disadvantage. Hard, usually because the other character walls extremely well, in Mario's case.
35:65 represents heavy disadvantage. Very difficult, but still possible.
Anything beyond that indicates a great deal of match-up imbalance due to something like an infinite, a CG, a lock, or something that inequalizes the required player skill between characters.
I assume this is what the majority of the character boards feel as well...since the majority of character boards uses the "x5:y5" system.
Edit: Also, you know as well as I that these match-up ratios are estimations. That's why they're constantly being debated and updated as time passes.