7 Days To Die was really great in early Alpha but it didn't really go well.
H1Z1 was fun for the first three days, then it became boring and It's still pretty much the same, I dont like BR.
Day Z Standalone is crap compared to mod, but I can't call Day Z mod the best survival game nowadays so sorry Day Z.
Somebody mentioned Fallout, which is one of my most favorite single player series, so if It counts as a survival game, it really wins for me when it comes to SP.
Thinking about the best survival game I realized survival games sucks, most of them are more like farm for several days and then get your work ruined by other players or farm till you get bored. There's too many Minecraft + Day Z games.