Short answer: I don't know & I don't think there will be one that will provide an objective assessment due to the complexity involved and the lack of incentive.
Long answer: A metrics-based approach to pick a good host is a great idea. However, it will be hard to compare as there are a lot of factors (like cost, geography, uptime, support, web server platform, visitor count) not just response time that decide whether a hosting company is good. One of 2 competing sites that we compare could host its static assets on a CDN while picking an average-rated Host. Unless you factor in all these attributes, it would be like comparing apples & oranges.
For a subjective assessment, you may find these sites helpful - HTTParchive.org (which tracks response times & other stats for a large number of sites) & Netcraft (which tracks Hosting companies).