A few years ago I was invited to the opening of a Ruscha photo exhibition in Cologne. The exhibition was set up by the MOMA in NY (IIRC) and 5 people praised Ruscha in german and english (they managed to pronounce his name in 7 different ways). Ruscha was there, the Bechers were there.
Then the doors opened and we went to see the pictures. Two caught my attention: the sunset strip and a parking lot with multiple appearance of Ruscha.
The rest left me cold and I left with the impression: banality. Another artist who thinks he's a photographer.

Maybe I could appreciate them on an intellectual level if I were more into art history - but the pictures themself didn't move me.