I totally agree with you on Brian Johnson, I really don't like his voice. I must admit I like Back in Black but it just doesn't compare to the earlier albums with Bon Scott, which I absolutely love.
I agree that their music is repetitive but I love the few albums with Bon Scott. Of course the lyrics aren't great, but it's great 'get drunk and party' music and it has a lot of energy.
And I disagree on them wishing they were Led Zeppelin. They sound nothing like them and I don't think they even wanted to. Jimmy Page and Angus Young have COMPLETELY different styles, they sound nothing like each other.
And what I like most about Angus Young is his vibrato, which he got from another great blues guitarist...
And it's such a joy to see him play, so small but so full of energy
