If a title series consists of nothing but non-genre novels and an omnibus that contains only non-genre titles, then it is clearly a non-genre series. But we list it as genre because of that omnibus. An example is <a href="http://www.isfdb.org/cgi-bin/ea.cgi?831">Doris Lessing's</a> "Children of Violence" series.
Anonymous
A couple of additional examples occur with Nora Roberts, with both her "Chesapeake Bay Saga" and "Irish Hearts" series.
With the revamp of the way non-genre titles are handled, this is no longer a problem. Closing as out of date.