Listing style is normally used for source code listing, but to me the default font used is not so pretty for source code listing. Attached is a comparison between listing and verbatim.
Did you try \texttt? It's the teletypefont family, a fixed-width font. It should look better.
I agree the defaults of listings aren't that appealing. Usually I write something like
\lstset{columns=fullflexible,basicstyle=\ttfamily}
You might also need to play around with the identifierstyle, commentstyle, etc., keys if the style for your code uses these separately.
The columns=fullflexible keyval suppresses listings's layout thing that it does to make proportional-width text fit into a monospace grid; it's not necessary if you choose a monospace font to begin with.