There should be a server-list when you click on servers. All servers which have completed some type of registration, would make it onto the server-list. To make sure all your servers you play on are in one place, you can favorite servers. And if you like or dislike a server, you can give it a thumbs up or down. You could view servers by people online, favorites, likes, popularity, server visits, etc. You could also see what servers your friends are playing on (when the friend system is added). The upsides of this idea are that, now Minecraft is mainly about multiplayer and very few people even play single player, so updates regarding multiplayer are, in my opinion, more important. Also, online server lists use cheap voting systems where you can vote for a server online for in-server money or rewards, making online ratings not completely trustworthy. The downsides of this idea are that this would be a huge update, and would take a lot of effort. It might be hard or even impossible to list so many servers. The system could be hackable, and voting problems may still exist, even if at a much lesser magnitude. It still seems to me though that this update would change the multiplayer system forever. Maybe the update could be implemented with the friend system.
In-game Server List