N64: Main Yoshi
Melee: Main Marth Secondaries Fox, Falcon, yoshi and Ganon
Brawl: Main Marth Secondaries Yoshi, Ganon, Falcon, Mario
Smash U: Mains Yoshi and Cloud Secondaries Falcon, Ganon, Marth, Roy, Little mac
RIP Marth in smash 4 since the only thing that has improved big time is his looks so sad -_-
I like using Marth in 4, I just can't play him like in the previous games. I miss his old self, but he's not so bad if you get into the mindset of him being a whole new character you have to learn.
Marth's my guy for the last three games, and in the case of 4 I also like to play Robin, Palutena, Bayonetta, and Cloud. In the case of Melee, I also like to play Jigglypuff and Ice Climbers. Never played N64 much except at a friend of my brother's house a few times, and Brawl isn't my choice of Smash.
(RIP the arc version of Marth's neutral B. It was awesome to use in Melee but it never returned.)