I like this article for not just commenting on the respective ages of Romeo (around 17) and Juliet (13) and how you have to cast those roles relative to the actors' ages, but for going into a pretty cool history about how other famous actors have played the roles.
Basil Rathbone? 42 when he played Romeo.
Orson Welles was a 19yr old Tybalt, which the article comments "must have looked a little out of place."
Norma Shearer was a 34yr old Juliet, alongside John Barrymore's 54yr old Mercutio.
But who's the goofball quoted near the end who says that some people might call Romeo and Juliet one of the "lesser" plays? It's no King Lear, but it's no Timon of Athens, either, people.