I think it would be motivating to see how many people have a higher voting rank than you and watch your rank go up over time for voting more.
i think it wouldn't make sense because the people that have 500 as a streak will always be first, maybe votes per month?(tell you the # of sites you voted on and how many times)
Or vote because it gives you good perks/money/stuff and its good for bringing new members to EMC. Just saying.
Of course, there are people with voting streak 500 so they will always be first, until they forget to vote one day or lose their internet or something like that. Then someone else will be first... For the average person, their voting streak will increase over time and some people will forget to vote and renew the streak. So the rank will go up over time very slowly. Right now I have no way to know how many people have a higher voting streak than me... I suppose I can /p on every single player but that would take days. Am I in the top 100? Top 1000? I don't and can't know...
I'm generally not one for "competitive" leaderboards and the like, but I confess some curiosity myself over who's topping the voting streak chart. And unlike some other suggested leaderboards, I don't see any particular harm coming from this one - if anything it might help encourage people to vote more often. (Even without contests!)