2018 is the only one I've played and it was very good. I enjoyed the narrative & dialogue, there were some great characters, and the voice acting was excellent. And it was very pretty obviously.
As for Ragnarok, I was a little bit disappointed by the trailer. It looked like God of War (2018) 1.5 - a very safe sequel of the sort you'd expect within a single generation. Maybe that's a by-product of needing to get it running on the PS4, but if that's the case then I wish they'd made it PS5 exclusive and really tried to push boundaries.