Imperfect GM #4: Expanding Horizons
Imperfect GM
Either a group is willing to try new games or it isn't, there's not much you can do to change this. If playing varied RPGs is important to you then you need to create a group willing to do that.
Everyone who asked me this question had a similar situation: they were part of a D&D/Pathfinder group and wanted to play something different yet the other players were very hesitant to change. Where is this hesitancy coming from? Sometimes it's because players are wary of leaving their comfort zones, yet just as often it's because they don't have any interest in playing the RPG you're pitching. Even more likely is that they're just happy to keep playing the game they're playing and don't see any reason to make a change. All of these reasons are fine, yet for some players, often GMs, it is a source of tremendous frustration as they want to try other RPGs.
Yes, you can get a hesitant group to try a new RPG. It requires some begging and pleading. If you're the GM you have a little more leverage, yet it's less than you would expect considering how much your contribute to the group. With a few weeks or months of effort you can win a session or two for the new RPG, which invariably a few members of the group might skip at the last moment. No matter how well the sessions go it won't really change the group's focus as they will want to get back to the D&D/Pathfinder campaign. If you want try another new RPG down the road you have to repeat the above process in its entirety. This is not fun.
One of my mantras as a GM is to accept your players as they are, you shouldn't be trying to shape them. If your group is hesitant to try new RPGs they you need to accept this. This doesn't mean you give up on trying new RPGs, it just means you need to shift your approach. My advice is to create a new group.
I suspect in everyone's D&D/Pathfinder group there's at least 1-2 other players who aren't adverse to trying new things. Instead of trying to bring the whole group into the fold, focus on those you don't have to arm-twist. Yes, this could be a pretty small group yet there's nothing wrong with that, look at my old Duets column here on RPGNet. Make sure you communicate that your goal for the new group is to play different RPGs, set up a schedule, and stick to it.
Five years ago my wife and I decided we'd like to try setting up a new gaming group focused on indie RPGs. We set it up on Meetup.com and made it very clear D&D and Pathfinder would not be played. The group has grown and evolved considerably over the years, yet once a month we host an event with 3-4 GMs each running indie RPGs. We certainly have benefited from living in a metropolitan area with a rich roleplaying community, yet the way we set up the group definitely contributed to its success.
Setting up a gaming group is challenging, it's not an easy process. You need to know what you really want. When my wife and I set up our group we knew we wanted to focus on playing new RPGs. We knew we couldn't have D&D and Pathfinder in the mix if we were to accomplish that goal, which presented a challenge as D&D and Pathfinder are the easiest way to recruit players. It was a slow process, and a lot of work as I did almost all the GMing for the first two years. Eventually it clicked, yet that only happened because we had a clear goal that we were committed to.
It is a great experience to play with a group that's excited to try new RPGs, yet there's nothing wrong with players who are happy with playing the same RPG year after year. I speak from experience there is nothing to be gained by trying to force one type to be the other. This isn't to say people don't change preferences but let it be on their terms, work with the players you have the way they are - this is the path of least resistance.

