As a game developer, most of the time, we want our games to be heard of, to be talked about, to be played as long as possible. Think about, e.g., Skyrim, which was released in 2013, until today we still see the name popping up frequently in the medias. One of the quality to sustain its existence is its replayability.
What makes a game replayable? Ok. This is not a trick question for an answer like "having a replay button." A replayable game in this sense supposes to be a game which can somehow establish deep connection with a player whom is convinced and would love to replay it from time to time. Think about some kind of food which you occassionally miss it and hunger for it. Yeah, that is your deep connection with the food; the same thing we need in the game.
This question has been asked often in any game development forum. It is a big question which you can find research articles, discussion, or blogs easily by googling it. Different people have different ideas. Different time has different techniques. Here, I will not go in lengthy detail, but I would make a quick list and throw in some references.
1. Story telling
- Good narrative
- Many story paths, Many endings
- Faction specific storyline
Story telling, or narrative, is one of the choice can be exploited to make a game replayable. A good exmple, I would tell you to look into novels, movies, or tv shows. Like myself, I watch Harry Potter once every year, from the first episode till the last; it has been my tradition for almost 7 years now. Besides the reason that it is a good show, and I myself grew up with it, having many episodes released sequentially somewhat encourages audiences to re-watch. In game industry, this is similar as having expansion.
Another example a long the same line as having expansion, but can be somewhat easier to be developed, is "spin-off." By definition, spin-off is "a byproduct or incidental result of a larger project" (from Google). Even though spin-off is be a different product, if you design the spin-off to have references from the main series, this would enhance replayability of the main series; because the audience might not exactly understand the reference that he would need to re-visit the main series.
Besides those, the regular idea of having good narrative that can build deep connection with the audiences is funtamental that we should never forget. Also, providing many story paths, or ending like in visual novel games, or any game which a player choose a faction of which specific story is exposed to the player, can be considered in either this story-telling category, or game mechanics one.
2. Game mechanics
3. Community Involvement
4. Business Model