The blogosphere (such as it is nowadays) mostly ignored it because, as has been observed, in the blogosphere every day is Batman Day.
In the mainstream media, the gist of Batman Day articles was mostly, 'Hey, Batman's still around and currently cool!". In the geek media, the gist was mostly, "Hey, look how the normals are observing Batman Day and maybe we can get some swag out of it!"
But I don't think I heard anyone express the sentiment I wanted to hear, mostly because Batman is SO much a part of our current culture and has been for so long. Specifically...
Batman is most important fictional character created in the 20th century.
I defy you to name a more important one. All your private detectives and starship captains and temporary television characters and cartoon figures--is any one of them better known, better respected, better entrenched culturally across all media? No.
I could sit here and MAKE my case. But, frankly, I think popular culture and the media have made it for me over the last 75 years. Who are you going to challenge it with?
Superman? I don't think so. Certainly he is popular and well known and as the first (well known) superhero, he is template for all that follows. But while Superman is someone we can idolize he is not someone we can truly relate to. In fact, I have read estimates that Batman is twice as popular as Superman, and he certainly is more consistently so. There's a reason that sales of Batman comics are the yardstick by which other comic sales are measured. Movies, comics, television--Batman leads Superman, hands down, in all of them.
Mickey Mouse? Mickey Mouse hasn't been a 'character' for decades. With the exception of some one-offs over the last 20 years, almost all Mickey Mouse cartoons were released between 1928 and 1953. "The Mouse" is now merely an icon, more a corporate logo than anything. Well known, yes, but he has zero literary impact. Ask anyone what "Mickey Mouse" stands for and you won't get any answer other than "Disney" or "profit".
I don't think there ARE even any other reasonable candidates to oppose Batman at the most important fictional character created in the 20th century, and I defy anyone to assert otherwise.