They're even doing it on the same character. Ike's neutral B has a more vertical trajectory and rises from the ground. Marth's neutral B arcs over his head. The only thing they have in common is that they're chargable, and it's like comparing Mewtwo's shadow ball to Samus's charge shot. And @Matt Silver- Ike's side b is that wierd dash thing. It's nothing like the dancing blade at all.
It's not that I don't like the other FE characters. It's that I like Marth is really the most important character in FE, but people's blind biases against his status in melee causes them to try to find any kind of reasoning (even illogical ones) for him to be taken out, despite the fact that the majority of people like him. They say we only like Marth because he's good, but you can't blame us for liking a generally good character formula. We like fast swordsmen, fast swordsmen are normally good, the characters we like are normally good. It's a personal preference no different from liking a powerhouse like Gannondorf, it's just that speed really is greater than power in smash, so it becomes an issue. And besides, in case you haven't noticed, a character's popularity should be taken into account regardless of the origin of that popularity. Shiek was a very popular character in melee, and though there are a lot of people who simply like ninjas, there were definately some that only played her because she was good. However, those people still like her and that is popularity, which supports why she was brought to brawl. Shiek also had a lot less going for her regarding her actual franchise, so apparently character popularity was enough to get her in. Marth has that, plus all of the stuff I've mentioned, plus this
http://smashboards.com/showthread.php?t=123714. Marth has a lot more fans than Shiek you know, because he's also got two FE games in Japan that everyone loved. A lot of FE fans in America have found his games too.