I have traveled all around the world business and first class and I have flown with many airlines but I can only recommend few.
Singapore Air's first class is incredible but in my view too expensive if you can not redeem miles for the flight or upgrade. Its busines class is very good. I heard that they are replacing their business class seats now which will make them even better.
I am flying Germany - Los Angeles back and forth close to every month and I can highly recommend KLM's world business class (top deck) for connections between Europe and the States. Very competitive pricing as well.
My worst experience was flying First Class with Lufthansa ..
as well as Delta's business class.
From where to where do you want to fly ?
Mike