I completely understand your frustration, but we aren't going to add this. We have some of our thinking about this in the FAQ here: Why don't you list everything in order of best fuel economy?
It boils down to the fact that this site completely relies on honest reporting to work. So if we add any incentive to get to the top of a list, we'll get dishonest data. Anytime you add a leaderboard of any kind to a public site, you add a reason for people to cheat.
I know this is frustrating, and it'd be nice to see which users are doing best across various data points. But we feel very strongly about not providing ways for people to "win" at using Fuelly. We want the site to be about tracking things for yourself and sharing that info.