These are easy domains to develop and its a bonus GamerForum.com/net aren't developed.
Gaming names have lost some value but still undeveloped worth high $xxx+ Find a motivated end user and could be worth a lot more.
Developed all depends on how popular it gets, but there are plenty of sources of revenue for this type of site so loads of opportunities. Develop, build up a user base, then look to monetise (If thats the way you want to head).