This is how I see this:
First of all, Madonna was famous all over the world and her songs where everywhere. Here is Spain, for example, we know who is Taylor Swift but I don't see people singing her songs, buying her albums or dressing like her. It's like if she's admired for the success she has in the USA more than for her inpact in our country. Of course she made her shows here and was like "Wow, it's incredible how much people went to her concerts". She made 2 60.000 people concerts (120.000) that is great but the same two nights ACDC made two concerts with 70.000 people each night (140.000) and the news said nothing about it. It was like "We have to talk just about her". There are other artists here that get her success or even more but you only hear about what Taylor Swift does. All her "records" and all those things but you never hear her on radio stations or in a supermarket or in a car that goes near your house listening music very loud.
When I was young Madonna (and her work) was everywhere. And I remember even my grandmother knew who was Madonna (that bad influence for our kids).
I think Taylor has a great career, but is just because she's a good influence for people and they try to sell her as much as they can. Everything is so perfect around her... It's like living in Disneyworld. I think Taylor will have a problem if someday she makes a "mistake" and does something not bad, just a little incorrect... I think people won't forgive her. Madonna, on the other side was always the bad influence. She made what she wanted to make and that was a problem for a lot of people and that's why sometimes they don't recognize her talent. But that is what make her (and her inpact in sociery) so big. Madonna is the only artist that after something like "Sex" could still be there after 30 years (look what happened with Janet and her nipple, people don't forgive the good girls).
I think it's impossible to compare them because they are from different times and music industry is very different but I have one thing clear. What makes them different is that Madonna always have had people that love her and lots of people that hated her (and they help to keep her there, like it or not). Maybe Taylor has more people that loves her now but there's a lot of people that only feels indiference for her... And love always ends but hate...