If you're curious about who comes out on top when it comes to NoSQL databases, there are a lot of differing opinions and a lot of places to look. You can check out rankings like those that DB-Engines put together (look at the popularity change in Graph DBs), or a less competitive breakdown of features and uses like Kristof Kovacs' list. Or, for a more open-sourced approach, you can just take a look at GitHub.
That's what Memect's Awesome GitHub does (for all sorts of topics), presenting a nice list of NoSQL projects on GitHub organized by stars. It's nothing you can't find on GitHub yourself - just compiled neatly for you, all in one place. Each project generates a mini-profile, summing up relevant information like this:
(Screenshot from Awesome GitHub)
And by GitHub stars, at least, the rankings look different than they do in some other places. For example, the top four:
Maybe not the order one might guess - though the fact that this is GitHub, and not just a general survey of users, certainly has something do with it. Either way, it's an interesting look at the what's going on in NoSQL, and a useful little tool to help you do the looking.