What makes games unique is not storytelling. Games are, by and large, not the best medium to tell a story. The demands of the medium mean you either need to constantly break up the narrative for long passages of loosely related player action, or you reduce player agency to such a degree that the experience becomes more akin to a lavish theme park ride.
No, what games are good at is suggesting stories. The thing that games have above all other media is interaction, which is to say that games have systems. Systems that dictate the rules of a fictional world. Systems that allow the audience to prod the world and feel it push back. Systems are what make games into games, rather than movies with joypads.
The Last of Us is a beautiful piece of work, full of astonishing visuals, richly drawn characters and a story overflowing with genuine emotion, honestly earned. It's a polished gem of a game, the state of the blockbuster art. State of Decay, by comparison, is kind of a mess. The graphics engine can barely hold itself together, characters and objects lurch through the scenery constantly, the frame-rate stutters, and the script and acting are rudimentary at best. Judged on every expected storytelling criteria, The Last of Us is clearly superior, so why do I feel that State of Decay is the better game?
Probably because it has more interesting systems churning away under its rather ramshackle exterior, and they push back harder against the player. Every supply run, every mercy dash to find some lost survivor, could mean the death of one or more characters. I might take a gamble on snagging some building materials and lose everything. A car might be overturned in the middle of nowhere, forcing me to think on my feet to get home safely. I care about the characters, not because the script tells me to or because they're convincingly played, but because they're in the game world with me. They're part of my story, rather than me being an observer of theirs.