Limiting the number of authors in the references with IEEEtran

It seems like you didn't include all of the fields needed to make this work:

CTLuse_forced_etal is required to indicate that you actually want to shorten author lists. CTLmax_names_forced_etal Gives the maximum number of authors before it shortens the list. CTLnames_show_etal Allows you to specify how many names will be given when it does shorten.

Your bib-file entry might then look like:

@IEEEtranBSTCTL{IEEEexample:BSTcontrol,
CTLuse_forced_etal       = "yes",
CTLmax_names_forced_etal = "3",
CTLnames_show_etal       = "2" }

This will limit author lists more than 3 by printing only the first 2 authors followed by et al.

Finally, you need to include \bstctlcite{IEEEexample:BSTcontrol} in your document before you cite any references (right after \begin{document} would be ideal). It won't have the right effect if it appears down by where you insert the bibliography.

A minimum working example:

\documentclass[]{IEEEtran}

\usepackage{lipsum} % For some dummy text
\usepackage{filecontents} % To make the bib-file

\begin{filecontents}{\jobname.bib}
@IEEEtranBSTCTL{IEEEexample:BSTcontrol,
  CTLuse_forced_etal       = "yes",
  CTLmax_names_forced_etal = "3",
  CTLnames_show_etal       = "2" 
}
@article{paperOne,
  author = "Author First and Author Second and Author Third and Author Fourth",
  title = "Paper One Title",
  journal = "Awesome Journal",
  pages = "111--115",
  year = 2013
}
@incollection{paperTwo,
  author = "Author First and Author Second and Author Third",
  title = "Paper Two Title",
  booktitle = "Proc. of Collection",
  pages = "222--225",
  year = 2013
}
\end{filecontents}

\begin{document}
\bstctlcite{IEEEexample:BSTcontrol}

% Paper text
\lipsum[4]
\nocite{paperOne,paperTwo} % Cite the references you want to include...

% Insert bibliography
\bibliographystyle{IEEEtran}
\bibliography{\jobname}

\end{document}

This will result in the following (note that the first reference has 4 authors trimmed down to 2, while the second reference is allowed to show all 3 authors, just as specified).