I'd like to see which tracks of an artist are most often "loved" by users (not only the ones with the most scrobbles).
There is a difference between tracks which get a high number of plays (often it is because they are the first track on an album), and those which are more obscure but get a a high percentage of "love". - "Most popular" and "loved" are different concepts, same as with people!
I would base this feature on percentage - if 200 users love a track which has only 500 listeners it says more than if 200 users love a 2000-listeners track.
Track ratings would require a lot more work than what sietegatosrojos was suggesting. Last.fm already has all the data they need to show us an artist's most-loved-songs (by raw numbers or by percentage of listeners).
Most loved tracks of an artist