Two Gentlemen of Verona is considered Shakespeare's first play, which supposedly explains why nobody's behavior makes much sense.
Proteus drops the girl he supposedly loves, betrays his friend, threatens to seduce his friend's woman, and...he's not the villain. Huh?
The BBC version attempts to pull off the plot by making Proteus very young and confused. The Chinese silent film A Spray of Plum Blossoms suggests that Proteus (Bai) was not ready to commit to Julia (Zhilu), making his pursuit of Silvia (Luohua) the final act of a desperate playboy.
Still--the play has not been performed or filmed as often as other plays by Shakespeare.
I think the romantic triangle is exactly the mark of an inexperienced writer. Like killing off a character, the romantic triangle is an easy way to achieve conflict/find stuff to write about. I think writers like triangles (and dead characters) more than audiences do.Trolius & Cressida (specifically, the lovers' parts) seems to suffer from the same problem, though it comes near the end of Shakespeare's career. Young, inexperienced writers and aging, exhausted writers might have a great deal in common.
Luckily, we have plays such as Comedy of Errors that show what Shakespeare could really do when he spoofed himself.
Likewise, the best part of BBC's Two Gentleman is not the lovers but the Duke of Milan played by Paul Daneman. He has the ability that look entirely nonplussed by Proteus and Valentine, which possibly sums up the writer's own reactions.

