I've been hanging around GameFAQs for a bit and only recently decided to finally come over here, and I can say that this statement is so true. I was one of Robin's biggest supporters over there, but every time that I'd mention him (pre-reveal), I'd be shot down. "He's not the main character," "He only appears in one game," "He's not a Lord," "He's just another 'avatar,'" "No, because he's male or female!"
Under the impression that people were just blindly following Gematsu, I made a topic about if people actually would "prefer" Robin over Chrom and asked them to put aside leaks and probabilities and just give me an answer. I was so disappointed to find that Chrom was overwhelmingly winning and that most posters just said that "He's the main character, duh." TBH, the only real reasons I could see to prefer Chrom over Robin is if you really liked Chrom's personality or if you heavily favored pure sword users (two answers that weren't given).
Then, after the Robin reveal, a handful of people went back on their words and admitted that Robin was a much better choice. It's strange- even when presented with a completely unique character (not saying that Chrom couldn't be) and asked if they preferred to have a spell-slinging swordsman, so many people just blindly wanted Chrom and would accept Robin until he was actually shown. Yes, Sakurai did a much better job than most predicted, but even the concept of a Mage Knight should have moved people but it didn't until they saw tangible proof.