IMO, Storj (storj.io) is the most mature in terms of viability. The project uses blockchain for metering and economics of the ecosystem but uses a more traditional and practical architecture that make's sense for apps and companies to use.

They seem to be taking a more performant and practical(read: usable) hybrid blockchain approach.

I do like what Filecoin is doing albeit Filecoin is more academic/provocative and a few years away from viability, IMO.