It depends on your needs, like whether it has to be self hosted, vendor supported, open source, file vs DB backend, enterprise support, easy to use, etc.
We evaluated about 10 or 15 of them and ended up choosing DatoCMS, a small startup with wonderful features and a terrific editing UI and rich plug in system. Their devs were also very responsive. A bunch of small QoL features like built in imgix support and graphql and such sealed the deal for us.
GraphCMS was a close second, with a very strong data model and solid API, but our editors (marketers, not coders) preferred Dato.
There are a lot of good choices out there. The only one we had a bad experience with was the industry leader, Contentful. They were both outrageously expensive (which wasn't the case when they first started) and also didn't really want us as a customer. They wouldn't even seriously meet with us without a NDA.
