ABBA is going to beat them all because of the reasons you've stated. Their music is enduring and everlasting. They have sold 380 million records worldwide so far and they are now the 2nd most successful bands of all time behind Beatles, but since their music is extremely versatile and timeless, they'll last forever. ABBA actually would have scored higher than Beatles but they weren't as popular in the US as they were everywhere else. And that's because of two reasons - one the Americans don't care for music as much if they are from non-English speaking countries - be it sheer ignorance or whatever and second, ABBA didn't market their music enough in the US as they were really not into flying or into live concerts. They were more into studio oriented.
I must say though the few times the did their concerts, they absolutely nailed it. I've seen some of their performances on youtube recently and I was blown away. Here's a few...