Most games won't use anywhere near that many threads and benefit a whole lot more from faster individual cores so the 3600/3600X are better in most cases. The 2700X only makes sense in heaviiy threaded scenarios.
I would say that the 3600x is better. However, depending on his budget, he might be advised to go to a ryzen 5 2600 for around 120 dollars and use the money saved towards a better video card which will be more of a factor.
In fact, truth be told, a real value play if on a budget, might be to pick up a ryzen 5 1600 as those can be had for about 80 dollars. Particularly look for the 1600af as those are supposed to be essentially the same as a 2600 with a little lower clock speed and 1st generation memory controller. But pick one of those up and overclock a little perhaps and pair it up with a good video card and you've got a decent box.
However if you friend has a lower budget, then as I said, I'd go maybe with a 1600 or 2600 and use money saved towards a stronger video card as that will more immediately help games and fps.
What FPS is your friend aiming for or what Hz is his monitor? The 3600 can deliver more FPS but is your friend aiming for high FPS to work with a high Hz monitor? Will he be using a gpu that can take advantage of that extra cpu performance?