"2nd to none"--> Literally, it means that there is nothing better because it is number one. However, in everyday speech it is fairly equivalent to, "really good" or even "the best" or "one of the best."
It is an expression used to state one's opinion on a subject.
e.g.
The food there is 2nd to none. (talking about favorite restaurant)
I think the best smartphone is the iphone. It's 2nd to none.