Any kind of persistency leads to what is known as "grinding."
In the case of singleplayer, the grinding can sometimes be addicting, in the case of multiplayer, the grinding addiction is raised to the tenth power.
In short, it will indeed end up making more people play the game more, but in my opinion, it is not good.
To have ranked play, just have ranks of some sort for show, but don't have them give an actual advantage in play, in any way. The best games are usually the ones that can be played competitively, and for a game to have balanced competitive play, it can't have this sort of persistency.