While i expect Zelda will end up on top in the end, it's a bit odd that so many in this thread are trying to paint Horizon's initial victory as totally expected when it absolutely was not. Despite the PS4's install-base, only a minority predicted Horizon would sell as well as it has. It was a brand new IP releasing next to the latest entry in a legacy series about to get a push from a brand new console's launch. It was expected to do well, but 1.5m+? Not by many.
It's also worth noting that while install-base is relevant, they can't be compared linearly. 1 million PS4 users is not the same as 1 million WiiU/Switch users, etc. That Zelda also outsold every previous entry in the series, despite the 2nd smallest release install-base, should make the inadequacies of that comparison clear.
