The article addresses this part clearly: the "RP" in "RPG" doesn't really define the category, since most (all?) character-based games are "role-playing": in a racing game, you're role-playing a race car driver, in a military FPS you're role-playing a soldier, etc. But I wouldn't call those RPGs by any stretch of the imagination.
RPG has pretty much come to mean a very specific thing: quest-type game with turn-based combat. I would never think of Zelda as an RPG.
(As an aside, remember Super Mario RPG? They mashed standard Mario with the kind of RPG format I describe above... funny that they explicitly acknowledge the format in the title of the game.)
I disagree with the "turn-based". There are loads of RPGs which aren't strictly turn-based or even feature action-oriented battles. Games such as Final Fantasy and Xenosaga would fall into the former category (which really is blurring the line a bit because it depends on what you define as turn-based) while games such as World of Warcraft or the "Tales of" Series, which feature real time combat, either more tactical (WoW) or even in the style of Beat-em-Ups (which was essentially pioneered by Tales of Phantasia and became a selling point of the series as a whole).
I would personally define RPG as a game that features most the following:
- a story that isn't just background for the gameplay (like in many FPS, where the story is just an excuse for you to shoot stuff). This will most likely includes character development and other sorts of progression in the game world. (Zelda? Check.)
- some sort of combat system, whether turn-based, action-oriented or with strategic elements doesn't matter (Zelda? Check.)
- generally non-linear gameplay including sidequests. There's usually a red thread along which the main game progresses, but you can "pause" at almost any time and just do what the fuck you want - go explore, do sidequests, grind levels or equipment etc. (Zelda? Check.)
- character progression, through acquiring new items, abilities, levels, skills etc. (Zelda? Check.)
I kept this intentionally fuzzy because there are many fringe cases, such as Monster Hunter, which basically lacks the story (it's really just an excuse to tell you "go hunt monsters"), but is otherwise considered an RPG too.
Zelda definitely IS an RPG. I think it's partially due to being so special that many people don't like to classify it as such - they might feel like it takes away from the magic a bit.
a story that isn't just background for the gameplay... (Zelda? Check.)
Is there some hidden story mode for Zelda? Last I checked a princess got kidnapped and you go rescue her. That is the total extent of the plot. It is as paper thin as you can get. There is no character development. Outside of Link's ability to use a sword he has zero character. Gannon is an equally shallow evil wizard dude.
I agree to a point, but there's a reason I included "world progression" into that point.
I do have to admit I'm a bit biased on this since I've read a lot of supplementary materials which flesh out the games a lot (there are mangas for Ocarina of Time, Majora's Mask and quite a few other Zeldas), and especially the newer Zeldas (arguably starting with Majora's Mask[1]) do have a decent plot and story, even though it isn't as "epic" as the likes of Final Fantasy.
[1] Majora's Mask deserves a special mention because it's - perhaps infamously - a very non-standard Zelda. Most of its charme lies in the incredible amount of (mostly optional) character driven side-quests which range from funny and interesting to soul-crushingly depressing. I consider it my favorite game in the franchise for this reason.
I think "Action RPG" is a better term for a game like Skyrim, but RPG works too. I think the main point is that characters should have complex, D&D-style stats that should be more important than player ability -- i.e. if an expert with a level 10 paladin can consistently beat a newbie with a level 30 warrior, then you aren't playing a "real" RPG.
RPG has pretty much come to mean a very specific thing: quest-type game with turn-based combat. I would never think of Zelda as an RPG.
(As an aside, remember Super Mario RPG? They mashed standard Mario with the kind of RPG format I describe above... funny that they explicitly acknowledge the format in the title of the game.)