I don't know if someone mentioned this already but perhaps the issue can be examined in terms of needs and how these are satisfied (kind of like the requirements used in interaction design).

Gamers play games to satisfy certain needs. How many of these would be satisfied if they were to use their time on Wikipedia? Could gamification help? What if all of their online friends were present in Wikipedia as well? Would that increase the likelihood of joining?

From my experience, when I had a survey on Wikipedia and offered barnstars, there were certain Wikipedians that loved to get one and valued it. This is pretty similar to awards systems that one finds in games. Perhaps, a global achievement scale for edit counts and other metrics would increase participation and could even satisfy some of the gamers' needs (the recognition part found also in Maslow's hierarchy).

But, it all comes down to primary needs. Games provide entertainment, social opportunity and personal identity development (or role playing). Writing articles provides personal satisfaction and social opportunities (but perhaps less direct socializing). Also, the complexity of tasks has increased along with regulations. Rules for e.g., WOW are easily explained and forced upon players by the environment. When it comes to writing, restricting e.g., people to write in neutral point of view is not something that can be achieved by software. One has to learn npov along with writing itself.

I think you touch something important here, but achieving it will take some serious research to understand what both groups want and find a common ground.

Michael Tsikerdekis