Who did they influence in the '80's and '90's? Squeeze, Marshall Crenshaw, Crowded House, Fountains of Wayne, Moxy Fruvous, Oasis, Charlatans UK. These are just bands that come immediately to mind that I listen to often.
I'm not personally arguing that the Beatles transcend the ages, mainly because I'm not enough of a student of music history to say that with any authority. But their influence, success and skill are all but inarguable. Go read the entry on them on All-Music Guide (www.allmusic.com) - they quite eloquently explain how the Beatles transcended everybody else.
I have a 14 year old daughter and I'm very aware that the Beatles hold no particular interest to her or her friends. Again, though, aren't we back to talking about popularity issues as opposed to significance or skill?
I think it's quite possible that you don't understand based on being in a different musical universe than I and many others. Your example of Hank Williams Sr. is a good example - he's definitely not in my musical universe - there are clearly many to exist in and very few people can be in very many at once.