I consider them fairly comparable:
* They both have a very large corpus of garbage shows and films.
* They each have a small handful of quality shows and movies that shifts as their licensing deals evolve and expire.
* Both of them are increasingly bolstering their content with self-produced content that is mostly of dubious quality.
At least in my household we seem to use each service roughly equally (I'd say 40/40 with the other 20% going to HBO now and no other cable, tv, or video consumption).
You're also not giving Amazon a fair shake if all you see of value is The Man in the High Castle and The Grand Tour, I clearly get a lot of value out of my subscription and I have yet to watch either of those. Right now I see they have all of House, Sons of Anarchy, Star Trek (most/all versions?), The Americans, and many more; dozens of episodes of I Love Lucy, Mr. Rogers, and Sesame Street; and some great movies like 1984, Spaceballs, Charlotte's Web, the Indiana Jones movies, (all the?) Star Treks, etc.