I don't see how Roy could be worse than 5th. He keeps cropping up in the bottom 4 of these lists but I seriously just don't see it.
He has much better ways to circumvent his crappy traits than a lot of these other characters (like Ness, Bowser, Kirby, Pichu). A bunch of these characters seriously have like... one decent gimmick and then their whole character is absolute garbage.
Bowser is awful once you get past how good Up+B OOS is. Yes, Up+B OOS requires you sort of play around his shield with some respect. And it's lame. But he seriously has no other useful shield options so to speak of. Projectiles in general crush this character unless he's on YS. His approach is completely non-existent and his moveset & normals are a complete joke. His movement is terrible except on YS. Maybe Bowser is secretly like low tier (as opposed to bottom tier) if we played YS only but bleh. Bowser sucks.
Ness has cool combos, sure, but he literally has nothing else going for him. He cannot play a pillar game with DJCs. The frames do not work out. It's slow and horrible. He can do some swing jump nonsense but the reach it provides is not enough for it to be really good for challenging a dash dance or similar. He has terrible crouch options (slow, low range, will never work, etc), the worst standard grab ever, and no real shield game so to speak of (I hear nair OOS is supposed to be okay sometimes?). His only reasonably good options for movement are WD back and DD but those are nerfed by his awful grab and lack of good normals. This leaves him with...? Combos. But how does he get them started? Also, his recovery.
Kirby is horrible. He has no range, no combo game, no priority, etc. His only good thing is that he can crouch and then do a basic 2-step combo if they whiff into him (assuming he gets an up tilt). His d-throw is horrible and shakeable for tons of characters at like 40% (they land on their feet before Kirby finishes and get away from the follow up for free). He doesn't have another combo throw at all. His only other decent trait is that his uair is really strong but that's not enough because he's still slow, no range, etc. His recovery is horrific.
Pichu just doesn't do enough with his hits, has no range, is frail when forced to tech, chain grabbable by tons of characters, etc. He's probably better than Kirby and Bowser though just because he can throw > move on a lot of relevant characters and he doesn't auto-lose to Fox's neutral B + Y button. He also has no CC game and a pretty crap OOS game.
Roy has a crappy OOS game but he can actually crouch into things. His good movement game also helps him circumvent his crappy OOS game. His high grab range (and range in general) gives some functionality to his good movement (DD and WD). His d-tilt is a good normal and unless the opponent true CCs it can knock people over at fairly low damage, which makes it good vs fake CC. His combos aren't as good but his tech chasing is solid and he has better edgeguarding than most of the above characters. He's also got the range & priority to stuff approaches without the opponent missing in front of him, because he has some decent normals, a good grab, and side-B.
I think he's better than GaW too, personally. But that one requires a lot more effort to argue because GaW has a lot of awkward death grabs, solid set combos, a strong crouch, a decent set of normals (which buffs his WD game), and some other shenanigans that Bowser, Kirby, Ness, and Pichu lack.
Also, since we're on the topic of really incomplete characters I might as well throw in Yoshi. I thought Yoshi's parry was some godlike technique for a while but it's just more defense on an already super defensive character. Yoshi's parry feels like it's just a sidestep that happens to combo you if you run into it. Yoshi still has no approach and no real offense so to speak of. He relies entirely on you running into him and him netting a really good counterattack from it. That's my impression of the character thus far. This is not a good strategy vs people who have ludicrous punishment games on you (especially off grab), or those with good dash dances. I don't know Yoshi as intimately as some of the people here, but I'm somewhat disillusioned with him (at least in NTSC) as of late. I seriously don't see how he gets in.
