Hi Your sites are great! I would recommend that you create a facebook fanpage for each one, or even each game and advertise the fanpage on facebook. This is cheaper than advertising direct to your site and you can post to your fans and get more engagement from them, a bit like having a list. On the topic of lists, you could also get a lead capture with autoresponder on each website (give away a free game or some tips ) then you are more likely to keep the visitors that you do get. Youtube videos also work really well for me, and are great in the games niche. Good luck x
Fb boost ad, youtube video share, make trailers. attractive banners. Then look whether the keyword in your site is active, which people types in the search bar. Check seo and do more gaming related site promotions. good luck
When yo go to forums and other gaming blog talking about your site will not help enough. Best way is to stay in touch and communicate in your niche with where gamers hang out. Video marketing is huge at this point, play few games or show your site around on YouTube.
Try to join onto your relevant gaming website in order to ranking your gaming site. Also SEM and SMM may help you a lot.