Developers often talk about this issue. How do I convince someone that my game is a game they should play? What makes it different or unique from all of the rest? Is it cheap enough to get more players but expensive enough that they take its contents seriously?
Those are good questions, but I have no answers for them yet. Very general "marketing" style sells feel very tacked on (though it is a necessary part). What I propose is that the concept of "earning your players' time" comes from asking these questions MUCH earlier on in the process: the making of the game itself.
I get nervous when I rely too much on my "gut feel" style of development because it may not encourage you to improve the game's Time-to-Sublime ratio. One of the best strategies to accomplishing this is putting your game in front of living, breathing people. Thinking about that ticking clock that is the player's engagement should be a high priority, especially after they've committed to your ideas by downloading and/or purchasing your game!
One of the most common ways developers approach the introduction is by explaining their game's core as clear and concisely as possible within the first five minutes, i.e, a Tutorial. This is the most concrete example of respecting the player's time; if they can't understand how to play it without knowing anything about it beforehand, how can you expect them to invest more time in something that makes no sense? The key is keeping the learning intuitive and subtle. Inversely, your introduction should allow the player to learn the nuance of the mechanics as they use them!
More than just a "feature on the back of the box," you had better have a surprising element where the player is completely struck. This isn't just a twist — twists are predictable and temporary — the Jaw-Dropper is the guy that people are probably going to tell others about when describing the game; more often than not, this element is the beauty or extremely life-like-ness-y of your graphics/world. In the average non-AAA games, this can also be referred to as the "gimmick." (and I'm not pooping on use of an un-done thing, more like emphasizing why this would earn more player time) For the most part, games are really good at doing this one. However, if the Jaw-Dropper is used poorly or too maliciously, it will more likely hurt your game's budget of player time than help (e.g, Micro-transactions, Waggle-Stick Controls, Quick-time-events).
This is the grand-daddy player-time-earner; even though you can't apply a plethora of variety early on without overwhelming them, you are going to keep a player interested by introducing micro-sized differences in the strategy of the game. Re-examine a property of a mechanic the player already knows; chances are, you haven't utilized the full potential of the element, and you can use this to earn some more engagement. The true art of this time-earner is knowing when and how often you should apply it.
Sometimes, people are looking for something familiar to fall back on. Constant amounts of change within your world or having such a foreign world as to alienate your player means they will feel disconnected from the learning process of your game. This is especially true for players who have never played a game that plays like yours. Great Art usually demonstrates a knowledge of the norm before it takes those references and defies them. It can feel a bit sickening cater to "convention," but you need to keep in mind that gaming-literacy plays a big part in how a player approaches a new game.
When meeting The Tantalizer, you'll realize that she's derivative of The Varietor; she will make her presence known early on, but won't allow the player immediate access. This thing will occupy the player's mind until they finally understand what it is or how to retrieve it. This is often a weapon or upgrade that the player wishes they had, but you can also use plot and mystery in narrative to earn a small but fanatic sect of the time-to-earns. Using the Tantalizer can let your players drool at the chance to learn, but beware; the payoff MUST match the effort.
Now To Conclude
One problem with this idea is that each type of "time-earner" can be more or less important to you depending on your player's taste in games, so the only way to make it appealing to the largest amount of people is by doing all of these time-earners relatively well. Usually, developers will sacrifice Theme, Narrative, and Innovation by making their game "universally appealing" instead of approaching with the time-earning lense.
I'm still learning better ways to earn your time... I deeply respect your investment, and it is wholy wrong to abuse it. In my experience, if you "punish" the player for their time, the prevailing feeling they leave with is that their work was "for nothing."
There's a number of games that suck at these time-earners (let's face it, AAA are lousy at this, thus unfair to include them :P), so I'm going to list some indie ones:
Dwarf Fortress (Introductor) — press Esc to Quit was all I understood
Aquaria (Jaw-Dropper) — why am I playing again? snore
Super Meat Boy (Varietor) — any difference from "World 3" through "World When I Quit?"
Binding of Isaac (Butterman) — lack of consistency, reliance on randomness
Fez (Tantilizer) — low payoff for the effort of mystery
But being an ass is easy; here are some indie games I think are REALLY good at each:
PLEASE understand that this is also a matter of my taste in games, and that it's uncommon (though exists) that "one" time-earner will ruin a game.