My writer's group is a diverse group of men and women who, thankfully, get along famously. I think what makes our group work is that there are no big egos or petty jealousies. Success for one means hope for all. It also helps that we are not all writing in the same genre and, therefore, we're very much on our own career paths, which can't be compared to someone else's.
It makes for some interesting critique sessions. While most of us read a wide variety of books, it gets tricky to offer suggestions on a genre that we might not read and know nothing about. It has forced us all to stretch as readers, writers, and editors. For me, it's made me pick up books in genres I wouldn't normally read so I can offer more insight to my fellow writers. I believe we've all discovered that the same rules of good fiction apply regardless of the genre. All successful plots have the same basic elements: strong characters with plausible conflicts and motivations, personal stakes that are high enough to drive the hero or heroine to action and to sustain the work to its conclusion, characters who grow and change, and resolutions satisfactory to each particular genre.
By reading and critiquing such a wide array of writing types and styles, and knowing our job as a group is to help each other improve, also helps us improve our own work. It makes us appreciate the uniqueness of each genre and realize that each genre requires skill–and a lot of hard work–to achieve success.