A more comparable part would be the i9-9980HK.
not really, that's an eight core CPU (and also a mobile part). I'm very interested to see how the lower core count Ryzen 2s compare to their Intel counterparts in single-thread, but part of what's so impressive about the (early) 3900X/3950X results is that they offer this kind of performance with more cores and at a consumer-friendly price point.
you're right that Skylake is an old design at this point, but intel invites this kind of comparison when they can't manage to ship an HCC version of their latest tech. entirely fair, imo.
Unfortunately larger and slightly refined Skylakes is all that Intel ships these days on Desktop. If it’s unfair to compare Ryzen CPUs to that, then I’m afraid there is no fair comparison that can be made until Intel gets around making actually new CPUs.