The best something can be, there is no phrase in the world which emphasises the quality of an object/person/situation more than top notch.
Stuart: How was you're date with Lucinda-May?
Edgar: It was TOP NOTCH!
Stuart: Woah, that means that it was better thananything else ever?
Edgar: Yes, because that's what top notch means.
Best and better than the in competition. First used in 1848 when reffering to a lady friend. Notches in the bed post were used to keep a record of the women you slept with. If she was the top notch then she was the best in show.