I obsessed about this kind of thing for quite a while when I started tracking my rides; ultimately I came to the conclusion that ride data of this type is only useful in large aggregate, compared like-to-like on specific segments short enough to limit error from external factors - and even then, it's only useful as a general guide to your overall performance, not as a competitive rating. I think the kind of analysis VeloViewer performs on your data is a fairly good implementation of this principle.

If you want a competitive metric, the only honest option is to actually compete. I like to think I'm a moderately heavy hitter in the local Strava rankings, but actually coming out and racing timed events has shown me that I've got an awful lot to learn and to develop athletically before I'd be heavy hitter in real competition.