I think 2-1 is WAY better than 1-1. It's just a more solid case all around and the ending is really brilliant. It's still kind of a short, unmemorable tutorial case, sure, but I think 2-1 is more solid.
I think PW2 is honestly really close to the other games in the trilogy in terms of quality. PW1 and PW3 probably only beat it out for me because they have five cases each and PW2 has four. 2-2 is a really great and really underrated case, and 2-3 isn't as bad as everyone says it is.