As Tenki said, a lot of people thought he was amazing because of his killing power. I post at a Fire Emblem board, and when Brawl was released here, people there went CRAZY over him. (Ironically, nobody cared about Marth beyond Ike > Marth posts.)
Then there's the fact that people cling to his stupid quotes like they're the second coming of your god or a lack of one.
Then there's the fact that he is (was) incredibly popular in those first days, and I swear that for at least two weeks straight, there was always at least one Ike player in my WiFi battles; two or three wasn't unusual, either. ALL of them played the same scrubby way. I don't mean to insult people's playing styles (well I just did), but honestly, if you just played a level 9 Ike + all of the scrubby players, you'd know at least half of what Ike could pull off.
THEN there's the fact that this board sucks. Not to troll or anything, but most threads that I click when I make my once a week trip to this board degrade into a flamewar full of pointless arguments and Rok the Reaper. They're terrible, and if you're looking to get any real hope from Ike players, this isn't the place to go.
I'm not excusing those who mock Ike players who actually try to play him effectively... but I am saying that the ratio of noobish players to Ike players with a decent strategy is vast compared to most characters, based off of my own personal experience.