For that refresh rate and resolution both the 1660ti and especially 2060 are overkill
I would kind of disagree, especially they want to run the most demanding AAA games at high graphics settings, and plan to continue using the same card for a few years. Already there are some games that can dip below 60fps at times with these cards at 1080p resolution with max graphics settings enabled. And if one wants to enable raytraced lighting effects in the few games that support them so far, they will generally be looking at a below-60fps experience even with an RTX 2060 at 1080p. Anything less than that will tend to drop below 30fps with those effects enabled.
Certainly one can get away with a less powerful card at 1080p if they are okay with lowering graphics settings a bit in some of the latest games, but there is room to benefit from that added performance. It's also very possible that games may become more demanding after the next generation of consoles come out, which are likely slated for release next year.
As for the initial question, I agree that I would rather have the RTX 2060 with a Ryzen 2600. The graphics card will tend to have more of an effect on gaming performance than the CPU in most titles, and the per-core performance of the Intel part is only slightly better, especially if the Ryzen part has been overclocked a bit. The 2600 has SMT as well, making it the more capable proocessor at heavily-multithreaded tasks, even if that doesn't apply to the vast majority of existing games. Either way, unless one is gaming on a high refresh rate screen with high-end graphics hardware to back it up, they likely won't notice a performance difference between these processors.