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.
Yeah, it definitely looked more like an expansion than a sequel, graphically speaking. It's especially disappointing that they didn't go all out and make it PS5 exclusive since they are now suggesting that it is the final game in the Norse story arc, as opposed to it being the 2nd game in a trilogy. I suppose using this approach did allow them to develop it faster though, it is looking like it will release a bit more than 4 years after God of War 2018, and that is with Covid taken into account, it probably would have only taken 3 years were it not for Covid. A proper sequel built from the ground up for PS5 would have taken at least 5 years with covid taken into account.