Zelda is not an RPG. Take a deep breath; sit down if you need to. I have heard people make statements in the past about the Zelda games being their favorite RPG. Sometimes I bite my tongue; sometimes I don't. Twice this week I have heard someone refer to Zelda as an RPG, so it's time to put this piece of knowledge out on the table.
An RPG is a game in which the player takes on the role of a character. The choices that the player makes effect what will happen to the character. That second sentence is the important one. Almost every game has the player assuming the role of character. If we let the first sentence alone define the game type, games like Call of Duty would be an RPG. Basically everything except RTS and puzzle games would be crammed into the category.
Zelda lacks the ability to make choices outside of a predetermined story line. You can't have Link make moral decisions about situations that will make the game go in one direction or another; the story is completely set forth without variation. You will go to temples, you will fight bad guys, you save the princess. Zelda is an action game.
A solid example of an RPG is Mass Effect. Players take over the role of Commander Shepard and determine whether or not they should be a good or bad guy, what type of fighter they should be, where specialties, both combat and personality, will lie, and even who will live and die in the story. Other games that follow suit would be Final Fantasy, Fallout, and Elder Scrolls.
Its just a friendly reminder of game categorization. Now, next time you hear someone refer to Zelda as an RPG, you have a solid response. A little knowledge to start the new year off on the right foot.