I don't know about killing infantry with sword cav (whenever I play that, I usually rely on sneak attacks or killing people who are distracted by melee), but I play lancer and can easily kill a skilled, aware infantry player 1v1. I just go in, slow down at the last second, and turn left as the lance is at its maximum extent.
Now, there are some tricks infantry can pull that work well: the best one is to use ~ to watch the cav player while walking in the opposite direction, then spin around and stab him with the bayonet as he comes in for the "easy kill", but that can be countered if you're expecting it. And, of course, infantry can just block down, but if they try that I usually come back around for a couch (although a skilled player should be able to tell whether a cav is making a stab pass or a couch pass). Trying to jump in front of the horse only works to stop couches; it's an easy kill when you're going for a stab.
However, the best way for an infantry player to defend himself is to get in good defensive territory: it's very hard to lance someone in a narrow alleyway, and almost impossible if he's got someone helping him. So in a city or a close group of buildings, infantry definitely has the advantage 1v1. But the worst thing for cav, if we don't restrict ourselves to melee, is the guns. A loaded gun is the best defense against cav: if you are any good at aiming, you can kill a cav coming in for a lance every single time. The problem (for infantry) is that they get impatient and try to shoot while I circle at a distance, waiting for them to do just that before coming in for the kill.
I don't claim to be a master player, but I usually top the charts or come very close as lancer, getting around 2:1 in TDM. Most of the times I die, it's either because (in order) I a) got shot, b) got my horse shot and got stabbed on the ground, c) misjudge the timing, d) get reckless while trying to kill someone who looks oblivious or who is reloading, or e) make an unwise tactical maneuver like charging into a dense group of enemies.