Human, IMO the free games from Sony and MS are taking a toll. Not only does that devalue all games, it means people spend their time on those. At the end of the day it's competition for peoples time more so than wallets, and if many of those people can game for free, they will.

PS4 March: Valiant Hearts (77%), CounterSpy cross-play (64%)

XB1 April: Child of Light (82%, and one of my favorite games of 2014), Pool Nation FX

X360 April: Assassins Creed IV Black Flag (86%, and the best AC in recent years), Gears of War Judgment (79%), Terraria (81%)

This is a very solid line-up of free games. I recall Black Flag on PS4 taking me 50% hours for a very enjoyable 100%, and Terraria is time sink for those into that genre.