Funny, I have similar anecdotal evidence. I haven't looked at the actual stats for my particular playgroup recently (which is admittedly not typically highly skilled), but our best player plays mainly Captain Falcon and just dominates. It may be more of a function of him just being the consistently best player, but suffice to say I was shocked when he was so low on the "tier list." Meta Knight has also never been a massive threat in our group. And then, I can dominate 9/10 times with Zelda and Toon Link (Zelda, too, is embarrassingly low on the "tier list"). Again, I admit that this may be more of a function of us generally not playing on a very high level, with me being one of the top 2-3 players, ha. But FFA is definitely a whole different beast any way you slice it.
MetaKnight is terrible in FFA (in my extensive, though still admittedly anecdotal) experience. In fact, since that's my playgroup's primary mode, we were tickled pink to learn that he was top tier in tournament style play because he's not good at all outside that very specific role.
In fact, we'd get a bunch of irregulars who would come over and play with us pretty frequently, and 80% of them would main Metaknight or Snake. The Metaknight players would get thrashed and they couldn't understand why (Snake was still very competent in FFA).
And Ganondorf is allowed to shine in FFA. You just take a more reserved approach, stay out of the fray, get more aggressive when you notice other players with high percents. The use of items gives him a better approach and more options too.
EDIT:
Just for shits and giggles, in our specific playgroup meta, Captain Falcon and Luigi were "top tier" (best stats after thousands of hours of playtime). Isn't Captain Falcon somewhere near the bottom on the "official" tiers? And yet he's incredibly suited for FFA.
You're not going to get a good idea on how FFA with all items on truly works in a "balanced" way when everybody isn't trying to abuse the potential of their character to the fullest extent they can. And using stats given to you by the game doesn't say anything about the character... other than win streaks or whatever. Win streaks aren't enough evidence to go by to determine whether a character is good or not. Especially in the case of items, which randomly spawn, the item that appears is random, and where the item spawns is random. Then you have the move set of the character itself, coupled with their attributes (weight, fallspeed, mobility, recovery, range, priority, character size, etc.)
You can't go merely by win streaks and assume "oh well that character must be good then"... no... the player could have gotten lucky off of an item that spawned next to him, could be playing better than all of you in general (thus player skill being uneven in the group of players and thus having no bearing at all on showing that the character is "good"), or other elements could have happened like three people letting the fourth guy KO all three of them at once.
Ganondorf is inherently a bad character with or without items. He has no positive attributes about him, he has zero mobility, zero range (forward air is not a rangey move in Brawl), he's a tall character (thus gets easily hit around and stuffed out of everything), and his recovery is absolutely abysmal. You could argue his weight is a positive aspect about him, but it's not enough to make up for the many faults of the character and items don't suddenly make all those attributes go away at all. An item spawns once every such and such time and during the time an item has not spawned, Ganondorf is still the same shitty character he is in comp. play.
The reason someone like Captain Falcon might appear better with items on is because of his mobility. But outside of that, he is still the same character as he is in comp. play. He still cannot combo off of any of his moves because of the inherent gameplay mechanics and his priority is bollocks (worse than Melee) in a game where the most prominent character is Meta Knight and the only way to beat his attacks is by having moves that are both fast and meaty. Falcon has no moves that are both fast and meaty to actually trade with MK and even when he gets a hit in, he can't capitalize on it because of the knockback his moves induce. And with being able to cancel hitstun with an air dodge, it just cripples him even further from being able to do anything.
Items don't even allow you to combo if you know the simple basic thing of hitting the L or R button the moment you are sent flying. Hitstun in the previous games at least allowed items to be enjoyable in the sense that you saw people going every which way if an item happened to be in the general trajectory of where someone was sent flying. Something like Snorlax couldn't merely be air dodged through like he can in Brawl (ignoring his overall screen size being shrunken even further from Melee...)
I'm not saying that items don't help at all; they do but only situationally. It's during the downtime there is no items that the character(s) will suffer. And if they have shitty mobility? No chance they can get the item unless it spawns right beside them. (Which can happen)
Items and FFA doesn't really shuffle the stronger or weaker characters around very much because the core of the game are the characters. Their potential lies primarily in how they are designed and if they are slow, more often than not, the faster character will get to the items first and dominate how they should. Hence why someone like Meta Knight is hardly affected by items and someone like Ganondorf might be hurt even more by them being there (it means giving someone like MK even more of an adv. in the MU than Ganondorf... and as it is the MU is already hugely disadvantaged).
What a mouthful of a post but yeah I hope that all makes sense... ^_^;
