State of Decay is an amazing open-world GTA-style action game.
Undead Labs' State of Decay is a really great zombie apocalypse game that blends a GTA-style (or perhaps a more appropriate comparison: Dead Rising-style) control scheme with a randomized, very dynamic mission system, where missions pop up and disappear every once in a while, sometimes forcing you to prioritize and make difficult decisions. This intensifies as the third major part of the gameplay, the base-building, comes into play. You are part of a group of survivors (and can switch between them), and are responsible for all parts of their survival - which includes ensuring a supply of food, medicine, ammunition, fuel as well as materials to construct defenses from. But due to the unpredictability of the zombies inhabiting the county you reside in, you may end up facing tough choices - do you expand into Marshall at the risk of leaving your base open to attacks from zombie hordes marching in from the north? Do you help a stranger in need or would you rather spend your time clearing infestations? And what if one of your people gets the plague? Can you live with putting a bullet in someone you just spent hours leveling up? Yep, nobody claimed zombie apocalypse was easy.
What makes choices like these even more harrowing is the fact that once someone is dead, they stay dead. That means if you play very badly, you may end up with very few survivors and a close to zero chance of making it through the next night. The fatigue mechanic also makes it impossible to concentrate on a "one-man army" tactic. Even the strongest survivor has to sleep every once in a while.
The biggest problem I've got with State of Decay is that it can end up taking all of my spare time. Personally, I take that as a sign of a really excellently crafted game.
Also, the graphics probably aren't going to win any awards anytime soon, but they're in no way hideous (except for a fair share of texture pop-in).
If you'd like a Dead Rising with looser time constrains (though not by much), a GTA with more zombies or a The Sims action game, you may just find State of Decay to be up your alley. But beware: It just may take up all your time!