Firstly, considering that Mario is called Mr.Nintendo and nearly every gamer on this planet has played a Mario game, I'm concluding that Zelda isn't as popular than Mario, I know plenty of people that have never played or even heard of a Zelda game, yet have played Mario. Secondly, as Badmuffins stated, it's highly unlikely for Nintendo to allow someone to make a Zelda film considering how badly the Super Mario Bros. game turned out, it gave Mario a rather bad name and was a joke of a film, no matter how many people try and say they like it because they are Mario fanboys. Mario also has the major advantage that he actually does have a voice that we've heard actually talk, Link however, just grunts, he never actually says a word. Therefore, imagine how hard it would be for them Director/Producer/Who ever decides who the actors are, to actually find an actor that looks like Link yet has a voice that people will find realistic. Personally, I think they will never find a good enough voice actor to give a Zelda movie a good name, there are probably a few people out there who have the voice to match Link's and recieve good criticism.
As you can see, personally, I don't think that they should make a Zelda movie, I believe that it would make Zelda appear as a joke to many people like the Mario move did, that film was so bad it was unbelieveable, so I say nay to a Zelda film.