I don't tend to do zombie games, or shooters anyway, but I have to admit even I think that State of Decay 2 looks really mediocre. Maybe it will look better on release for having been delayed.
Saying that - I don't think it's a fair comparison really - Detroit is a big AAA title with amazing graphics, but very niche gameplay, exploring very controversial topics.
State of Decay 2 is a generic zombie co-op title, which basically hits all the current trends - co-op multiplayer shooter with zombies, so even though it's just a sequel to a low budget arcade game, I think it may sell equal amounts to Detroit, despite far lower production values. Look at the success of PUBG.
I'm interested in Detroit because I see it not only as a beautiful game with impressive motion-cap, but as one of those games that push people's perceptions of what video games are. I love games that push boundaries and have novel themes or gameplay. I love the idea of my choices making the story. The amount of work done on Detroit is staggering, I read two years of writing for the branches. I personally don't think "kill zombies" is comparable. Also I'm a weak willed woman and Jesse Williams is delicious!