I have only flown F and C on LH, but I am satisfied with the product.
Transatlantic, I have flown Y on LH, AA, TW, and the US Air Force. I would rate LH at the top and the US Air Force at the bottom...
On short flights (less than 2 hours) in Y, I have flown AA, BA, CO, LH, LX, NW, WN, and UA. I would rate CO or LH the best in terms of overall quality, but WN does what they say they do - cheap seat on a plane that gets there on time, so would consider them successful in their market.