Crap, what is it with you people and tiaras? So Marth looks a little feminine, it's really not a huge deal. I know it's just your personal preferences and I'm down with that. But think about it, do you honestly think Sakurai will be sitting in his studio as his crew is working on the game, and think...
"You know what, I'm going to scrap Marth. That tiara always bugged me." XD Sorry, I'll stop being odd now...
On topic: I know this is probably an oddity on this thread, but I have never played a FE game before. However, looking through this thread and taking a look at both characters, I'll say this.
I'm cool with Marth returning, he and Roy (okay... probably mostly Marth XD) were largely responsible for us in the US of A finding out about FE in the first place. And he did have a nice move set, I know it was fast, but I don't think it was overpowered, not to mention the small sweetspot on his sword, as mentioned before, kept him from being broken.
HOWEVER...
I am intrigued by Ike as well. I'd love it if they were both in, but if I had to choose one, it would have to be Ike if solely because of personal interest and preference in character design. Like I said, I haven't played a FE game before. So that's that.
P.S. Oh yeah, and I'm all for the Black Knight being in Brawl too. Ganondorf should use his sword, but he also needs magic. BK could be a heavy sole-sword character.
Not to mention I'd love to run around with the BK in Brawl yelling, "Come on, you pansy!" and "Tis but a scratch!"