What genre do games like 'Dear Esther', 'To the Moon', or 'Gone Home' fall under?

Such games have long been established in Japan where they are commonly referred to as Visual Novels.

First-Person Exploration Game.

Where most first-person games wind up being shooting-based (hence an entire genre for those games), these games largely follow the same interaction style of those games, but cut away the 'shooting' aspect in favor of exploration and interaction with the environment.

Now you could say that First-Person-Shooters can also have a wide degree of exploration, and you'd be correct. In these games however, the primary action is in exploring the game, rather than shooting things in the game, so Exploration becomes the defining part of identifying the genre.

The Stanley Parable is defined as a First-Person Exploration game, and it's a very good name for such a game (which bears similar gameplay style to the three games you've listed).

According to wikipedia :

• Dear Esther is qualified as First Person Art Video-Game
• Gone Home is qualified as First Person Interactive Story (which I think suit better for the genre)
• To the moon was nominated "Best indie RPG of 2011" which tend to prove it's an RPG.

Those games are quite rare but First Person Interactive Story describe the first two quite well.

First of all, a word of warning. Everyone out there uses different genre taxonomies, so there can be no "right" answers to questions such as this one. Some of the bigger taxonomies out there are found on Wikipedia and MobyGames, but both of them are highly inconsistent and self-contradicting. Please also note that loads of actually existing subgenres have never been named anywhere.

While all that is true, it's still interesting to explore in what ways the mechanics differ between these games and where they fall into the existing gaming ecosystem. So I hope the following assessment will still be valuable for you.

The first question one has to answer is whether these specific games are adventure games or not. Now, following Ernest Adams in Fundamentals of Game Design Wikipedia defines adventure games as follows:

An adventure game is a video game in which the player assumes the role of protagonist in an interactive story driven by exploration and puzzle-solving.

So, the requirements are a story to progress through (while the term interactive is used, this does not mean it actually can branch!), and that you progress through this story by exploring the game world and solving puzzles in it.

Wikipedia also lists specific components of adventure games:

• Problem or puzzle solving
• Narrative
• Exploration
• Player assumes a role
• Collection or manipulation of objects

Now, what's really interesting here is that it seems as if puzzles are a must-have component of adventure games. However, defining it like this results in lots of problems. For one, there is no main genre which encompasses narrative games without combat and without puzzles, so if games without puzzles are not adventures, we are in need of new main genre (Interactive Story?). Also, imagine a game like Secret of Monkey Island, but strip it of all puzzles. You just progress through the same story with the same point and click interface. Is that really a different main genre (e.g., a difference as big as between shooter, RPG, adventure and fighting games)? I'd argue not, and recently have been similar arguments in the community (e.g. see http://www.adventuregamers.com/articles/view/24000/). You'd also have to come up with an artificial barrier between both main genres. Where do you draw the line between interactive fiction and text adventures then, if only the latter is an Adventure?

The bottom line for me thus is that puzzles might not really be a necessary part of adventure games.

Anyways, on to your examples. IMHO they fall into different subgenres:

Gone Home tells a story, has light puzzle elements and object manipulation and uses a first-person perspective with direct avatar control. As such it is clearly part of the adventure genre. Other than having only light puzzle/object elements, it isn't all that different from other direct-control first-person adventures. I call these First-Person Adventure, although that term has sometimes been used for the Myst type of adventures employing indirect point and click control (which I have another name for).

Dear Esther tells a story, has no puzzles, extremely light object manipulation and uses a first-person perspective with direct avatar control. Whether you still call this an adventure or not depends on the puzzle problem I explained earlier. If you think puzzles are mandatory, you obviously need a different subgenre for it. You could call it First-Person Story. If you don't think puzzles are needed for it be an adventure, you could still call it that and make it a different subgenre of adventures. Or, you place it in the First-Person Adventure subgenre like Gone Home, arguing that this is just at the extreme low end of puzzle-density of that subgenre.

To the Moon tells a story, has puzzles, has object manipulation and uses a third-person top down perspective with direct avatar control. It clearly fits within the Adventure genre but the change in perspective makes for a vastly different gameplay experience, warranting its own subgenre. I call it Direct Control Adventure. Actually, this is nothing new. Other examples of it would be Escape from Monkey Island and Grim Fandango.

"Walking games"

i.e. They don't emphasise many of the most conventional videogame activities, such as shooting things, solving puzzles, powerups or defeating enemies. Instead, the one mechanic that they do prominently contain is that the player walks around from location to location.

If you had to summarise 'Dear Esther' as quickly as possible, 'A stroll around a Hebredean island." would be a pretty good start.

Hence, I've heard these referred to as 'walking games.'