Help choosing a gaming laptop

My pick would be the MSI, partly because of the 8GB of VRAM (and G-Sync). It probably has the best keyboard of all three, too. While the 4K display of the Acer sounds nice in theory, you're going to have to play AAA game titles at 1080p anyway to get optimal frame rates. It also lacks G-Sync, unless I missed something.
The ASUS seems good, but only has 4GB of VRAM.

I think they are all excellent choices, and you wouldn't go wrong purchasing any of them.
While my personal choice is the MSI, yours may be different than mine. :D