LogFAQs > #906656922

Marth and Ike's chargeable B moves have completely different properties. Marth's is a thin horizontal rapier-like poke that breaks shields. Ike's is a gigantic blue flame (three pillars in Smash Ultimate) with a huge vertical hitbox and spike properties that damages him if he uses it too long. If your logic for movies being similar is as simple as 'they charge' then you can make a lot of characters in the cast look like clones of each other.

Actually, let's compare all of their moves.

Similar:
Down B (counter)
Down Smash (forward then backward slices close to ground)
Up Air (circular slash above head)

Either Way:
Side Smash (circular forward slash, although Ike's is significantly slower and has a different windup animation)
Dash (circular forward slash, different speed and windup animation)
Forward Air (circular forward slash, different speed, reach, and windup animation)

Different:
Neutral B (already explained)
Side B (chargeable dash slash that can cover a huge distance vs. repeated quick strikes at melee range(
Up B (Aether vs. instant upward slash with sword extended horizontally)
Neutral Air (sword swung in huge circular arc around body vs. two quick horizontal slices)
Back Air (horizontal slash vs. circular slash)
Down Air (vertical spike below body vs. circular slash below body)
Jab (punch combo vs. quick circular slashes)
Up Tilt (holding the sword perfectly horizontal with a square hitbox vs. quick circular slash)
Down Tilt (horizontal swing close to the ground vs. very fast small poke)
Side Tilt (horizontal swing at chest level vs. circular swing)
Up Smash (huge slowish circular hitbox vs. quick vertical rapier-like poke)

Not comparable at all. They actually have a lot of distinct differences that the varying hitboxes of the sword allow - for example, Ike has the generic 'horizontal hitbox behind body' that like 70% of the cast has while Marth's is circular.
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Black Turtle did a pretty good job.