Melee's biggest flaws (not in order):
1. IC's chaingrabs and wobbles.
2. Sheik's no lag tilts and chaingrab-KO/gay d-throw combos on almost every character.
3. Peach d-smash.
4. Fox's waveshine combos, shinespike.
5. Falco SHL, shine combos and pillaring.
6. Certain chaingrabs (Marth vs. spacey on FD).
7. Zelda's d-air..........(joke
)
Other than that, I think the game is pretty **** well balanced from Fox on down to Ganon/Link or even DK. Also, a lot of what I just mentioned can be countered with good DI, tech skill, spacing and mindgames which makes it even more balanced.
I think although Melee has some irritating unbalanced things, it's a brilliant game where the better player often wins regardless of character. You get someone on a platform or on the ground they can:
1. Get up.
2. Roll.
3. Tech in place or tech left/right.
4. Sit there and do their get-up attack.
On a ledge:
1. Ledge aerial/B move.
2. Regrab ledge.
3. Ledge get-up attack.
4. Ledge roll onto stage.
5. Hang on ledge.
6. Wavedash onto stage.
Get grabbed you can:
1. Wiggle out if possible.
2. DI the throw and hope for the best.
3. Spot-dodge the grab attempt.
Thats pretty much the essence of smash except in-game the calculation is very fast and based on experience and probability. Good players will recognize which action has been taken or will be taken and react accordingly with the best aerial/dodge/B move/shield/grab, etc. possible. Of course they also know how to combo so they choose the best aerial/rhythm of fastfalling and L-cancelling to maximize the damage or combo potential to set up the next hit/KO/edgeguard/whatever. Watch a recent vid of Ken, KDJ, PC, etc. and if you know anything about smash you'll see a genius at work.