Take a look at this (top player tier lists)
https://docs.google.com/spreadsheet...cz7Tza8MqyZU9gZVJIa25T2qo/edit#gid=1184642298
Versus this (tourney rep rankings)
https://docs.google.com/spreadsheets/d/1AJs-mj5TTdkmkl7nhj4twJymVPTLTUdT0MBToL1cxDs/edit#gid=0
Here is a presentation of a comparison between character tournament representation and character tier ranking:
Most characters will have tourney representation fairly close to their numerical tier orderings. Notice, for example, Lucina is the 6th most common character to see in a tournament, and she is also ranked 6th on the tier list. This represents a perfect agreement between top player tier list rankings and a player's actual representation in competitive play.
There are some characters with very large discrepancies, however.
Joker is 22nd in tourney rep, but ranked 2nd. This is likely because he's quite new, and hasn't had nearly as much time to establish more scoring on tourney rep yet.
Other characters, however, have been around since the game's release and still show tourney rep that's out of line with tier rankings. Pikachu is 24th in tourney rep, but ranked 4th on top player tier lists. Pichu is ranked 17th, but is actually way more common than Pikachu, ranking 7th.
Ken and Ryu are vastly under-represented for their tiers, and so is Marth. These characters are ranked solidly mid tier by professionals, yet have extremely low rep. Marth's case may be, to some extent, due to the abundance of swordfighters, and better options being often chosen over Marth, such as Lucina. The characters are so similar, Marth's playership may be so low due to Lucina overshadowing him.
I don't have a good hypothesis for Ken's low tourney rep relative to his placement. Nor for Ryu.
King Dedede is ranked low tier by professionals, coming in at 59th. He, however, is 31st in tourney representation. This is the fighter with the largest, positive discrepancy between their tier placement and their tourney representation. Donkey Kong is a close second, coming in at 63rd in tier placement, but 37th in tourney rep.
These two characters may merely be popular and fun choices, as I know a lot of people seem to enjoy playing these particular characters. Ganondorf is also a bit over-represented, coming in at 45 on tourney rep, yet 56 in tier.
Here's a better visual on tournament representation as a function of tier placement:
This is an exponential regression, mapping total tourney rep percentage as a function of tier.
I'm actually not totally sure an exponential regression best captures the trend in the data, as it seems many of the higher tier characters actually have representation above the fit, whereas the lower tier characters seem to all be along the curve quite tightly. A power regression may have been better (but that requires a MATLAB toolbox I don't have and I don't know how to compute it without it, which makes me sad).
Nonetheless, you can definitely see some of the characters I mentioned above are above the line. It could be suggested that these characters are either popular and overplayed, or are placed too low on the current tier list, as their actual tourney rep is a definite defiance of their placement on the tier list.
One piece of data I'd like access to, but don't currently have, is some way to obtain actual playership for each character. Then one could try and adjust this for character popularity. After all, simply playing online, I can give my own anecdotal 'evidence' to the popularity of ganon, dedede, falcon, dk, and ness being way more common to encounter than characters such as wii fit, ryu, ken, marth, diddy, and other characters that show up here as being under-represented for their respective tier placements.