The ones Samsung has been making for the past year or so are pretty good - displaymate says they are nearly as accurate as the Igzo IPS panels Apple was using. A lot of what you're seeing when you see the "unnatural" OLEDs isn't the panel sucking it is the colors being deliberately oversaturated by the OEM - a lot of Android phones come that way by default. Even Samsung was doing that the first few years they had AMOLED phones. Those of us who like accurate colors don't want that and think it looks horrid, but I guess there are a lot of people who prefer that look since it is more 'dramatic'.
I have no complaints with the panel in my X, I looked at the same photos side by side with my 6S plus and the colors were identical. It is nice seeing true blacks instead of the 'very dark grey' regions where black should be if you're in a darkened room.