How is it possible to main two characters as different as Roy and Samus? I cant even pick up a secondary with any success, because whenever I play as anyone except Falcon I suck, get discouraged, and go back to playing Falcon, and that includes characters that have a similar style.
You'll get people who say you 'can't' have two 'mains', people who say you can, and whatever in between, but it just takes some focus and practice. The three characters
I tend to bounce around are Mario, Link, and Luigi. I know a little bit how to play others as well, like Lucario and Wario, but I've put hours, upon hours, upon days, upon months of time into Mario, Link, and Luigi individually.
I think the secret is, in a large part, dedication. If you find yourself hopping from character to character without really sticking with them, you're never going to find the tricks, the nuances, the ins-and-outs that you're going to need to succeed outside of your comfort zone. Going from Mario to
Luigi was such a huge and drastic change for me, that I felt the same way you do outside of Falcon; I dropped it, I quit, I couldn't take how slow and floaty he was. But, then, I decided to start watching some games, reading up on his character, and I began to improve. Learning the Wavedash for Weegee improved my game for Link and Mario as well, just like learning L-cancelling early on with Link helped with Mario and Luigi.
What I'm getting at, is just take what you know with Falcon, and try to apply it to character that you didn't even think his skillset could glean anything from. Try to push your boundaries, and get outside of your comfort zone. Spend some time doing nothing but watching and reading about not only Falcon, your main, but a character that you might be interested with. Heck, give Ganondorf a try; I'm sure it's come across your mind or been suggested before. The movesets will be similar enough, but the
playstyle will be so drastically different that you'll go through an experience adjusting to that. Like I said, try spending time
out of the game learning about the game, and whatever you do,
don't quit.
Don't bounce around, character to character to character; if you don't stick with it, you're not going to find something that you can
play comfortably with. That's what my roommate's friend has trouble with; he'd come in, switch characters
every day, and complain every time that my two roommates and myself
always outskilled and outperformed him, even though he played roughly the same amount of time as the others.
I've made this wall of text too big as it is, so I'll sum it up: blah, blah, blah. Something, something, dedication, blah. Just get into a groove with a character, and
stick with them. I promise you'll do a lot better if you just stick with it.