Personally, I like the marth matchup. The key to beating Marth in my eyes is patience. It's like, he's right there and you just wanna hit the guy, but if you rush it, then he's got you. That's what he's wanting you to do.
Delays. I don't know how to explain it well. But you gotta get close enough for him to commit to an attack: FAir, FSmash, NAir...and you still have to be spacing good enough for him to miss, and sneak in a Bair, Uair, or FAir, Ftilt...something. Like, jump at him, almost come within his range, when you know he's gonna forward smash/air, and then use your double CAREFULLY, spacing in mind, and after baiting his attack, counter it.
In this matchup, ganon has to counter marth. Marth has quicker aerials, a tipper, super easy edgeguards vs Ganon, and he combos Ganon easily, as does everyone. When Marth's playing right...it gets tough. Sometimes you'll take 3 licks to get one. So you HAVE to make the best of every hit. Once you get marth off the level, please please please don't let him back on. If edgeguarded correctly, he doesn't get back on at all.
All in all, you gotta space the BAir outside his FAir range. You gotta get him to commit, and capitalize with a counter attack, and use little delays to mess with his attack timing. It's a guessing game in the air alot of times...so you gotta trick the little bugger. Be smarter than him. Use platforms for spacing, tricks, delays, all of the above really.
Yoshi's story used to be called Marth Land around these parts...now we call it Ganon land. It's my favorite place to fight marth. When used correctly, the platforms are more useful for us Ganons, than for marth. If not used right, we get smoked.
