The Witness is a 5 hours long game if you don't rush it. So far, No Man's Sky didn't show anything that would make me go bananas for it. The hype has deflated a lot since the original unveiling. The Witness is really not a good comparison because that game is akin to The Order, meaning little gameplay and replay value "for a cinematic experience". I couldn't care less about that in my medium.
This thread keeps delivering.