I voted for Ike for a few reasons. First of all, I like the Fire Emblem games a lot; they have a unique style, and they really test your tactical skills. Of course, they'd be a lot more fun if your characters didn't die permanently, but on the bright side, they wouldn't be so good for developing patience if they weren't so frustrating. Ike's probably not my favorite Fire Emblem character, but he's pretty high up there, and he's a good representative of the series.
Secondly, Ike just has a great image. I mean, ya gotta have blue hair! He's tall and commanding and makes Marth look like a sissy. He has an awesome cape and a gigantic sword, and his moves all look really cool.
Finally, Ike is a well-developed, noble character. As Fire Emblem Path of Radiance begins, Ike is just a young rookie mercenary working for his father, the leader of a successful mercenary company. When his father is murdered, Ike must replace him as the leader of the mercenary company. In time, he avenges his father, becomes the general of a mighty army, conquers an evil empire, and grows into the greatest warrior of his time. Throughout these events, his character, like his swordsmanship, matures and develops as he confronts tactical, ethical, and personal dilemmas. In time, he develops courage, confidence, strong convictions and ideals, and an iron sense of selfless responsibility. But what I really like about him is that even when he becomes a general, he remains true to himself and unimpressed by position or social status, treating those above him no differently than his friends that he grew up with. In sum, Ike tempers all of his attributes with true honesty and humility, and I think that makes him my favorite character in Smash Brother's Brawl.