Chester Bolingbroke on the three elements that must be well-balanced to make a good computer role-playing game: breadth, depth and immersion.
Breadth refers primarily to the physical size of the game. It can be measured in dungeon squares or tiles, or in modern games the length of time it takes to travel from one end to the other. It also refers to the length of time it takes to play and win the game ...
Depth refers to the things that you find and to the things that happen within that game world. The specific elements depend on the game's genre, but for RPGs it includes things like the backstory, lore, NPCs, quests, and character development. ...
Immersion deals with the game's capacity to make you feel like you are truly "occupying" its world, and it's primarily a function of graphics and sound--although we must allow for skilled developers who can engage the player's imagination in the absence of these things, as a good author does.
This is a great way to understand the limits of modern open-world games like Skyrim and RDR. Objectively they are deep compared to older games, but their vast annd realistic breadth creates a sense of relative shallowness that limits immersion and gives the uncanny sense of being stuck in a theme park full of robots.
Pictured is the map of Fate: Gates of Dawn, a 1991 Amiga RPG that exemplifies the problem with excessive breadth. Every pixel is its own square, and you can explore it all—but every step of the way, you're trapped in a 1991 Amiga RPG.