Odds are its a play style difference you unaccustomed to. As samus, you had fairly good range in SSBM, and you potentially played a camping oriented style making them approach. Tournament worthy is a wording that makes me wonder if it was good enough, but you never went to tournaments. If that was the case you may never have had to deal with a good marth, a character that can out range (not projectile but out range) samus. Like marth before, olimar has a move set built around the strength of range, he is able to hit you before your close enough to hit him theory. What this requires from opponents is adapting and developing ways to win like others have mentioned, either staying far away from either players range using projectiles/camping. Or you have to figure out clever effective ways of moving inside of olimars range to your own range, and connecting with a move. I was a marth first in SSBM, but as i picked up a couple other characters I faced the same issue, I was not used to having to figure out how to get inside the range of another character and safely reach my own shorter range to land moves.
Thats a lot of theory and development that i'm sure if my guesses are correct you'll want to learn, if nothing else for the future you'll better understand characters with less range than you and how they move in. If this isn't the case sorry to waste that time, i'm sure it helped someone though. Rather than ramble on about more style theory though, a few quick hard tidbits to put the pressure on olimar to adapt are these.
Approach diagonally, its not the easiest way for many characters, but UpB is not a natural choice for nearly any olimar, and is actually one of the most punishable moves when used incorrectly, so make your opponent try and use it, its the only easy answer to being approached diagonally.
Learn the hitboxes. Pikmin are sorta weird, and can throw people off. However they are a lot like Falco's reflector. Just cause it looks like its still there and a hitbox, doesn't mean it is. For instance pikmin don't grab on their way back to Olimar, only on the way out. Also learn the timing of FSmash, they are still live hitboxes as they fall, creating a somewhat weird drawn out almost pause in the hitbox, you don't wanna charge in too soon after it, but know when in the fall they are no longer able to hurt you. Its not easy, but focus on olimar not the pikmin, see when the lag is. Its far to easy to focus on the pikmin coming at you, which effectively distracts you from Olimar and what he can or cannot do.
Lean to gimp the recovery. With everyone getting used to Brawl and its changes, ledge guarding is changing and evolving, but most importantly different. However, a very SSBM like style can hurt olimar considerably by simply grabbing that ledge asap. Learn to look for it, learn to create opportunities for it, learn to abuse it.
Notice the pikmin colors he has. No blue? don't be afraid of grabs as much. A lot of purple? Realize his range is going to be shorter than normal. I'm not saying you have to memorize the order and strengths of all the pikmin to play against him, but being aware of it can seriously help.
Find priority. Olimar doesn't do well against it, and while many of his moves offer a solid priority, once you find attacks that can punch through pikmin, use them. I'm personally not familiar with samus or what moves can do this, but I don't doubt they exist. This requires Olimar to change things up, have better timing, or in some cases use less common and less strong moves in response.
That should be more than enough info to sufficiently overwhelm you for now. If you manage to employ all of those tactics and your still losing miserably, your friend has simply gotten very good with olimar, I'd love to see it and hear about it, even if it is working with you on how to overcome it. Good luck,
-True
. Lol jk, well im no pro player but I think that to beat olimar you need to keep the pressure on him, his pikmin (if they grab you) damage you until u attack and kill them, or until they fall (not sure how much time they stay on you..
. Keep pressure on him, and wathcout for his incredibly ranged attacks, once his off the stage simpli gimp his recovery (by grabbing the edge) and he's done..
