Tiers are, at least supposed to be, an overall measure of the metagame. Basically, how much of a threat a character presents. They are normally supposed to be based [not completely reliant] on tournament results, the ones that matter, of course. Which is also why tiers shift. This, of course, assumes people want to win, and will pick the characters they are good at. However, some games try to do it differently [I'm pretty sure Melee does]. Pokemon looks ONLY on usage and usage alone, which is the only example I can think of straight up metagame.
However, making a tier list like that for SSB64 would be stupid. It'd look kinda like this:
Fox
Falcon
Pikachu
Mario
Kirby
Jigglypuff
Yoshi
Link
DK
Luigi
Ness
Samus
So, a character should be ranked on how good they are, and given how small SSB64's scene is, it's VERY hard to debate such a thing. Very often, we're throwing darts. But it makes for good discussions. XD Makes the boards seem a little less ded.
If you disagree with decent combo ability and Ness having priority, and the projectile stuff [minus Link, I forgot to mention Link], you're on drugs. XD I do not know myself how does Ness' priority compare with Kirby's [on some moves, on all, Kirby wins]. Like was said, I'm throwing darts, Ness vs Kirby matches are hard to come by unless I'm playing nubs on EGX, I have a friendly and someone who never uses Kirby uses it, or I fight Matts.
Also:
in my opinion, DJC isn't terribly effective when you don't have Yoshi durability in the 2nd jump
Ness doesn't get Yoshi's durability with DJC, but combos better [at least at a lower level] with it. Against Kirby though, durability matters more.
The only area Ness would be able to beat Kirby is with priority. By that, I mean, IF Ness has more priority on some moves. I don't got AntD's gear. XD
And, I agree with Koro, cept he didn't mention dair spike, which pales to Kirby's and the only usage he has over Korby is DJCing it. XD Also, usmash is a combo move for Ness, so I disagree there as well. FSmash is poop.