This is true. Mathmatically 1/2 health in a fighting game would equal 1 stock in melee, because of how the rounds systems work, which you explained below. Now then, do other fighting games have combos that take away more than half of your health?
Yes they do.
1/4 of a health bar equals somewhere between 1/3 and 1/2 of your stock.
If you go by the minimum number of rounds then (assuming the same player wins all matches)
2 lives per round times 2 rounds out of three equals 4 health bars. 4 stock per round times 2 rounds equals 8 stock. 1/4 healthbar=1/2 stock in this scenerio.
However, if you go by the maximum (assuming you go back and forth)
3 lives per round times 5 rounds equals 15 health bars. 4 stock per round times 5 rounds equals 20 stock. 1/4 healthbar=1/3 stock in this scenerio.
So, lets say that on average you live to about 90-100% in melee (excluding gimp kills). This means that a 1/4 health bar combo in another fighting game would translate to a 30-33% combo in melee. However, that's for small mistakes (like spacing slightly off so you don't sweetspot0. The bigger mistakes (missing laggy attacks while close to your opponent) recieve much more punishment.
You should also not be able to escape punishment after a single hit, which does nowhere near that 30% I listed above. Is a guaranteed three hit combo cruel and unusual punishment? What happened to the whole "don't get hit" philosophy. You know, the idea that mistakes are bad and that you should strive for perfection?
And most of the time you don't have a full stock advantage. Most of the time you're at somewhere between 60-80% when they die, which is an easy advantage to overcome. You come back invincible for a full 2 seconds, giving you ample time to give yourself an advantageous position. What you're referring to, is the 0-death combos, which is about the same as a 1/2-2/3 HB combo in any other fighter. That kind of advantage is hard to overcome in either game.
Just as if you combo me to 50% I can come back with a zero to death and use good DI to live past the 100% death zone.
Oh really
http://www.youtube.com/watch?v=7lIcE_-tWv8
Yeah, I'm pretty sure you still have to work a little.
That's only if you have a full stock lead. That would be similar to having a 1/2 HB lead in a fighting game.
That's a reward for me whiffing an attack, and then having predictable or improper DI.
Not only that, but it only happens when the attacks that you whiff are laggy enough for your opponent to successfully set up such a punishment. How often does Marth get zero-death'd from missing a fair? You allowed your opponent to land a particularly useful combo move. If the opponent has a large array of such moves, then it is a character balancing issue, not a game engine issue.
Or, you can stop making assumtions about my game preferences. You assume that I want to play a game like SF, when I like smash specifically because of it's unique system. Percentages instead of life bars means that good DI can actually make you live longer, and good prediction can actually make your opponent live shorter (health wise). The general freedom of movement and edgeguarding dynamics also have very good appeal.
But then again, this is all personal opinion, so don't divide the community over yours.