My Ike vs Marth matches make me think the same thing as the threadmaker. Honestly. Ike outranges Marth, he outpowers Marth, and outspikes him. Also, Aether > Dolphin Slash. There's a bunch of things Ike can do with Aether. Recover, Aether-spiking in two different ways at the edge of the stage, combo it with dthrow, and more. Dolphin Slash is only good for slight comboing, recovery, and gimping some characters' jabs.
Plus, Marth is extremely vulnerable if Dolphin Slash misses. Ike, not so much. He gets super armor, plus Aether finishes up quickly.
Another thing, Ike's Counter > Marth's Counter. Marth's comes out faster, but Ike's has the advantage of doing more damage and lasting longer.
Next, I find it a lot easier to spike with Ike than Marth. Haha, that's so funny. Spike with Ike. lol. Anyway, Ike's spiking is so beastly it isn't even funny. He can gimp edge-canceling with dtilt, combo dair with a bthrow or fthrow at the edge of the stage, or Aether-spike two ways. One, while Ike is recovering, resulting in a backfire on a possible edge-guard attempt, and the second way, which is harder to pull off, while Ike is facing the edge of the stage and the opponent is away from that stage edge. Ike even has a fourth spike known as Eruption, although this is the hardest to pull off. Even I'm not positive if my success-look-alikes in the attempt to do it were true successes.
Really, at most, this match up is 55-45, Ike's favor. Ike's only disadvantages are Marth's speed and Dancing Blade. Also, if a Marth can pull it off, Ike is screwed if he manages to start edge guarding him with fair.
I'll end this post by saying you all should remember that this is coming from a player who uses both Ike and Marth frequently.