This is an interesting thought. I don't know if you have kids, but I have two girls and a wife--all three couldn't be more different (my oldest is an alterna-chick who just did a National History Day project on the Riot Grrrl movement), my youngest is a typical suburban middle school teeny bopper and my wife is obviously older than all three with tastes that are different. All three of them absolutely adore Taylor Swift to an unhealthy degree. As far as I go, she's really grown on me--I like most of her stuff.I don't think I could tell you a single Taylor Swift song off the top of my head that has come out over the last ten years, or since Shake it Off. I don't listen to pop music really though, and I'm sure I'd recognize some of her bigger songs over that timespan if I heard them, but I couldn't tell you their names. As big as Swift is, and you can point to her concert revenue and social media influence and all that stuff, it's hard for me to believe she is bigger than Michael Jackson, as Klosterman said, simply because pop music isn't nearly as ubiquitous as it once was.
I was knee deep in all things Michael Jackson back in the 80s as was my brother. We were obsessed with the guy. But the difference between Taylor Swift and MJ (at least in my two families) is that my Mom knew about MJ but never listened to him--aside from when my brother and I would play Thriller. I don't think my Dad knew anything about MJ.
I think--and I can't prove this--that Taylor Swift has deeper penetration into other demographics other than just the youth. Older people, like me and my wife not to mention my mother, know who she is and can probably name somewhere in the neighborhood of 10 songs. At this point you almost have to jump over MJ and wonder if Swift is approaching The Beatles or Elvis Presley territory.