For ryzen you'll want 3000 or better. Youd still see a gain on the intel side going with similar speed. On my 7700 system I got fairly large gains going from 2133 to the xmp profile of 3000. Gains were across the board. Cinebench, 3dmark as well as actual gaming.
The issue with this upgrade is the cost. The used market on the k sku 67/7700 is crazy. $250 plus easily, unless you can find a crazy deal. The non k sku are slightly less, but still overpriced for such an old cpu. Youd still be upgrading to a 4c cpu vs ryzen with at least 6. And new prices are higher than used for the i7.
And your gains will NOT be worth the cost. I did 6600k to 7700, but I got really lucky. My work was recycling pcs and they happened to be 7700 based, so free cpu for me. Would I have been as happy with the upgrade at a price point of near enough $300, absolutely not.
If you can a deal, do it. But I wouldn't pay more than $100 or $150.
Do plenty of research on this upgrade and consider all options. But from my personal experience, if you're going to pay that much, do a core upgrade.
Another note, if you do go the i7 route, make sure your bios is updated. 6th gen should drop right in, but 7th gen will require an update.
One other thing to think about is the fact that doom 2016 would basically run On a potato. So if the specs are similar, and your current hardware is up to running doom, I doubt eternal will give you issues.