Sheik probably got nerfed because Zelda got little attention, which is probably why Zelda got buffed. (I believe she did, anyways.)
I know! That's exactly how I feel! Now poor Samus fails, and got an undeserved nerf. In that case, Sakurai HAD to,
HAD to realize what he was doing.
A) Charge Beam is smaller and less powerful. In Melee it was deadly, in Brawl it's hardly so.
He probably did it so it would have faster charge time. Otherwise, agreed. I cry over this 
B) Super Missiles have terrible knockback. In Melee, I can KO with a Super Missile at 100%. In Brawl I can't even do it at 150%.
I can't KO with it at 300%
C) ALL of her aerials are weaker (although her zair is pretty good when you can land it). Even though her bair is useable still, and can KO, it's not half as deadly as in Melee. Even her Meteor Smash is weaker, although it still does the job.
Mourns over the loss of nair.
D) Including Final Smashes, Samus has this supposedly uber-powerful Final Smash, but it's slow, easily avoidable, and doesn't necessarily KO. It can, at most, KO 3 people once, and that's if you're facing some pretty stupid or unlucky (tripping, falling helplessly into it) opponents. With Sonic's, you can easily 2KO 3 people. Then, once you're done, you transform into Zamus, which takes so long that by the time you do any enemies you might've killed will be right at your side with a Smash Attack fully charged. Once you get out of the transforming animation and are Zamus, you've got about 3 seconds where you're helpless, giving your opponent plenty of time to Smash Attack you to the stars. And even if they don't, by using Samus's Final Smash, you're FORCED to play as Zamus, who doesn't even play remotely similarly. They are completely different.
I wish they were separate sooooooooooooooooooooo badly.
If Sakurai didn't realize what he was doing to Samus, he's pretty **** stupid.
Somebody on the development team who play tested Samus must've had melee fingers.
I'd say he nerfed her because Missile Spam and the use of Charge Beam was easy and rewarding, but Pit's Arrow Spam is pretty annoying too, so I doubt that was why.
I'm willing to stick with "He's a complete ***hole."
Agreed tenfold.
Mario- Tried to keep balanced, but failed.
Luigi- Tried to make better, but decided to give him poor aerial movement speed.
Peach- Tried to make worse, but she still has a good tier placing.
Bowser- Tried to make better, but still sucks balls.
DK- Made some changes, turned out good just to whoop MK and Snake.
Diddy- The fruits of Sakurai's labor. **** bananas.
Wario- Sakurai obviously doesn't know how people play smash. Too good.
Yoshi- Tried to make better, but still sucks horse feces.
Link- Tried to make faster, solid in all respects except speed and recovery.
Zelda- Tried to make stronger, well she's stronger but still slow.
Sheik- Tried to make weaker, well, she's weak but fast. Basically, they took the good qualities and separated them between the characters making 2 sucky characters, instead of 1 good, 1 sucky.
Ganon- Tried to make slower, they succeeded.
TLink- Made a very annoying to deal with, yet easy to defeat character.
Samus- Tried to make worse, WHYYYYYYY!?!!
Zamus- Sakurai knows nothing of physics. Less weight, more falling speed. Losing a gun and armor, more kill power.
Pit- Sakurai really, really knows how to break a character in more ways than one.
ICs- Tried to make easier to use. They can still infinite, but we already knew that would happen.
ROB- Most broken thing next to MK and Snake. Only difference is that ROB needs more skill to use.
Kirby- Sakurai's right testicle. Annoying voice included. Tried to make better, and succeeded.
MK- Sakurai's left testicle. Sakurai thinks that infinite combo ability, small frame, priority, recovery, range, and kill power is enough to compensate for a light weight. What about jiggs huh?
D3- Sakurai's object between the testes. It's pretty much MK with more weight and chain grabs.
Olimar- Plays most like an ssb64 character. Sucky recovery, but amazing combos, range, power,and priority.
Fox- Tried to make worse, solid character still. He just lacks priority and large hitboxes.
Falco- Tried to make worse. Near god tier er... I mean above god tier. He's Bread tier.
Wolf- Tried make an opposite of the other two. Still has poor recovery, still has good combos.
C.Fal- Sakurai is going to hell for this. No, he deserves worse. Sakurai's going to bottom tier.
Pika- Tried to make better, made the spammiest character in the game. Solid chara, though.
P.T.- Like Zelda+Shiek, only you divide the overall potential by 3 instead of 2.
Lucario- Tried to immitate Mewtwo. THINK OF MORE CREATIVE MOVESETS FOOL! Sakurai thinks that aura is enough to balance him. Maybe if aura affected priority...
Jiggs- Tried to make worse. He succeeded. Jigglypuff fans mourn.
Marth- Tried to make worse without getting the fans unhappy. Can I even call this a success? He destroys the lower tiers, but sucks against the top tiers.
Ike- Well at least he doesn't immitate Roy like Lucario.
Ness- Tried to make better. Didn't make good enough. Also forgot to program his grab release animation.
Lucas- Tried to make an Earthbound character for those who didn't like Ness' playstyle. I don't use him...
G&W- Tried to make better. Now he's broken to a whole new level.
Snake- Kojima programmed this guy himself.
Sonic- SEGA didn't pay Nintendo enough money.
