Characters that I think could end up (like in a year or more) being considered neutrals for C. Falcon, based on experience and how much potential I think they have in their moves:
Ganon: slow as can be, Ganon is fairly comboable for Falcon due to his slow moveset, although he will be quite difficult if he knows his shielding and dodging well
Link: fairly slow, fairly punishable; Link's got a couple moves that can be tough to deal with, but once you get past his camping game, he doesn't have much in the way of speed to hold you off if he misses
Samus: pretty much just like Link; ZAir can be a pain, but the missiles are pretty slow, as are her melee attacks
Jigglypuff: poor range; I have very little experience with Jiggs but it seems like the fight should be like Kirby without having to worry about the up-B, neutral-B, and Hammer. I'm not sure if Jiggs can gimp with DAir like Kirby does
C. Falcon: uh yeah, should be obvious
Yoshi: again, not much experience. I've heard Yoshi is pretty gimpable with footstools, but has some combos that could give you trouble. The biggest problems are supposedly BAir, DAir, and pivot grabs
Squirtle: currently a lot of disagreement on this one, but Squirtle's range isn't that great. If you can avoid getting combo'd and getting grabbed for a relatively low percent throw kill, you should do fine
Peach: Peach has a couple really good combos that involve glide tosses, her floating is really good, and her FAir is pretty much unbeatable, but otherwise not a tough fight
Mario: Mario's aerials can combo you all over, his cape can gimp you pretty badly, and his fireballs are sometimes really annoying, but I could see him as neutral due to the poor range on almost all of his moves
Ike: Ike's UAir is almost unavoidable if he times it right, and he can kill you at ridiculously low percents, but he is ridiculously slow in most of his moves. Avoid laggy moves so he can't punish you with anything too powerful and you'll do fine
Luigi: Luigi is a lot like Mario, but instead of gimping capabilities he has much better recovery
Lucario: Lucario's got some mean disjointed hitboxes, but none of his moves except DAir seem particularly powerful, so he could end up being neutral
Sonic: used to be fairly difficult for me, but jabs beat almost every approach. Definately not particularly hard
Wario: grab release stuff may evolve enough for this to be a fair matchup
G&W: very light, and FAir and BAir can often be punished if they miss. Knowing his moves very well will help you see what's coming, because he's not very fast
Zelda: pretty good moves, but they have enough ending lag to punish. A lot of baiting and you can win these
Diddy: recovery has long enough startup to edgegaurd effectively, the problem is how well he and you use bananas. From what I remember Dash attack picks them up (which really helps).
Lucas: DSmash and USmash are pretty strong but very laggy. PK Fire doesn't hold you like Ness's, which gives it a lot less potential than Ness's. Also seems to have a weaker aerial game. It's very hard for him to catch you with PK Freeze, and even if he does you can break out pretty fast. Punishing his PK Thunder instead of getting hit by it is very important.
Fox: As far as I've seen Fox is like Falco but weaker in almost every aspect, and his non-interrupting laser is almost useless against Falcon, who can close the gap pretty fast. Shine can't really gimp Falcon unless you second jump into it, since Falcon Dive always seems to grab him