As of 2015 I think it's quite difficult to say. However, I give the edge to Batman.
This is based on critical response and box office from the Dark Knight Trilogy and earlier films (both characters have at least one absolute stinker, Superman IV and Batman and Robin). I think more folks would go and see a Batman film than a Superman film.
I think that Batman has a slightly wider appeal, as despite the fact that he's a ninja/billiionaire/genius/detective/armourer/mechanic/scientist/master of disguise and a bunch of other stuff that would take about 50 lifetimes to master (and which makes him nearly as impossible as Superman), on some level we identify with his humanity, and on some level we believe we could all be batman.
Superman on the other hand, well we can aspire to his moral values but we can never fly - although we'd all love to.
Having said all that I really go back and forth. I identify strongly with Batman in many ways, but I love the noble spirit of Superman - that unlike any human, with the power to make the entire Earth kneel at his feet, instead he uses that power selflessly to help others.
And he's never said "I'm goddamn Superman !" I mean, Frank Miller come on. I loved your 80's Bat-stories, they're the best ever written but WTF happened to you ?
http://whatculture.com/comics/50-reasons-why-superman-is-the-greatest-superhero-ever.php
Anyway, I doubt there's much difference in their popularity really, but I still give the slight edge to Batman.
As for Spider man...... who's that ? Just kidding.
Just IMO of course.