I've had the game for just under a month now. I won't go through the trouble of nitpicking every single character at the moment, but instead I'll state(with facts) who I think will be ranked high and ranked low.
*know that this is just what is what at the moment, everything is up for change*
Lower Ranked
Captain Falcon: As much as people love him, the truth is that realistically he isn't suited to win tournaments. Ask anyone that knows what they are talking about in the Falcon forum, and you'll hear the same responce.
Yoshi: He could combo, I know. He could do a couple of decent things. But he has sooo many GLARING disadvantages that his decent things don't overshadow. I think it goes without saying that Yoshi isn't perfect.
Samus: Go to the Samus forum. Ask anyone who is drastically trying to make Samus better how good she'll be and you'll get your answer. Remember though, that Melee Samus's style wasn't developed for a while after Melee was released.
Ganondorf: Foward B is one of the best moves in smash history. But look at everything else, and it falls short. Too defensive with not much to back it up.
Sonic: I'm sorry fans, but really now. He has the most difficulty in the game killing certain characters. He has no reliable killing moves, and his edgegaurding skills are only subpar, his speed won't make up for it on a competitive enviroment.
Higher Ranked
Marth: This one goes without saying, I wont dwell into it much. Top? Probably. But nothing lower than high tier.
Olimar: He's a beast, he is the best camper in the game, has insane range on smash attacks, has a VERY LONG grab with almost no lag on it, and he kills very early and racks up damage fast. His recovery blows badly, and it'll prevent him from being top tier though.
Toon Link: Goes without saying.
R.O.B.: His tilts are so ridiculous that he actually is a very good counter character for Marth. He has great projectiles, his Backair auto-retreats him for no shield grabbing, he has a spike, his edgegaurding skills are unmatched, his Nair kills fairly early otherwise. Great recovery too. He's just great. Deny this, and your not looking at him right. High tier or higher mid hands down.
Luigi: Jab to firejumppunch is insane, and his aerial juggling ability racks up damage very nicely. He preasures shields so much and is pretty safe while doing so, and he has a great recovery and a mulititude of killing moves.
Wario: He's being overlooked SOOOO badly because of who he is. He kills super early, his fowardsmash is near broken with the fact that its super fast and has superarmor on it so it can't be stopped, great recovery, great edgegaurding skills, combos lead to finishers, preasures shields like no ones business, has an air grab, has the best aerial DI in the game, his grab game is among the best, he survives long but isnt a big target, he is really sincerely just beastly in the right hands. High or higher mid absolutely.
Metaknight and Pit: I'm catogorizing them together because they do indeed have many of the same slight faults and big ups. Both have a great recovery, have great edgegaurding skills, chain together moves very easily, are quick, and overall just very balanced and flat out good characters.
Snake: As of now he's been placing extremely well in tournaments and is simply great. Great camping, preasures opponents and has mindgames like crazy, kills extremely early, and controls stages. Overall he's just flat out great.
Ike: I might get bashed for this, but I always consider Ike as the Ganondorf(with a sword) in this game. He's dangerous. Ike's speed is way too fast for how strong he is, really. He plays great keep away, has a disjointed huge sword, kills very easily, he's dangerous to edgegaurd against too. There is a reason why Azen and many other great players have flocked to him.
Pikachu: Combos lead into kill moves, good recovery, speedy and hard to hit, very preasuring, and overall coming together very nicely.
King Dedede: Chainnnn graaaaaaaaaaabbbbb, scary edgaurding skills, great projectile, hard to approach as most characters. Has trouble with Marth, but ****, alot of people have trouble with Marth. Overall, he's great. I doubt he'll be too high on the tier list, but its clear at this point that he'll be on the better side of the characters.
Zelda: I'll leave this one to your imagination because I'm tired of typing, lol.
PS: Lol at tier list above me being completely based on nothing.