Violent entertainment in general is of poor quality and mass appeal. Young guys like stuff that is unneccesarily violent, be it music, movies or games, and the majority of entries in any of these categories is usually of poor quality since its mostly made for demographic appeal and with little intellectual substance. Music and movies have been around for a while so the many crappy, poor-quality songs and flicks dont really draw attention but video games are relatively new so we notice this more. I mean, i know gory games have been popular since the early 90's but the sophistication of the latest generation of gaming has allowed for more realistic violence that can now emulate its feature-film counterparts so there is an upsurge.

So its a trend, and it may temper down a little bit, but it'll always be around. Thats my take, anyway.