Do you have 20/20 vision? I've owned the original iPad, used the iPad 2, use a friend's iPad 3 daily and own the retina MacBook Pro. I also use, on occasion, a 27" Thunderbolt Display and non-retina 15" MBP.
Let me be clear, anyone who can't tell the difference is either lying or doesn't have on their glasses. It's not even close for me.
I had the same reaction when I got my iPad 3 and posted to that effect when people said on these forums that they couldn't tell much of a difference, but since then I've come to the realization that the average person just doesn't notice the difference much. I know dozens of people that own iPads, because of social connections I have, and I can tell you that the vast majority of them wouldn't notice the difference or even care. I have a couple of friends that are nerds like me and they feel like I do but they are the exception. I personally find it incredible that they don't see it like a bolt of lightening, but they don't.