Building sub-communities around specific games would be important I would think. Content about games has to be understandable to be interesting, so unless you're a player of a particular game, it's hard to be engaged by content about it. Within those sub-communities, weekly contests could be effective. Screenshot competitions like best cityscape 'photo', largest collection of a particular item, most hilarious killcam, etc.
Tons of gamers love achievements. Brainstorm ones you can create for games that the games don't offer themselves, that you can track on the site through self-report / screenshot upload / or being awarded by members of the community.
Activity on the site in general could be made to feel game-like. From profile-completion tracking, to leveling up based on contributions, to unlocking functionality / customizations. Have the first visit to the site each day provide progress toward a reward, and a small chance of getting a bonus.
Think about what your audience really wants. Fun? Novelty? Validation? Friends? Challenge?
Sticky is a function of giving them what they really want, consistently.
Ask yourself this: Is your app a vitamin or painkiller?
Painkillers have an obvious need, quantifiable market and can be monetized. Vitamins are more about emotional need, not efficacy.
Which do you think are Facebook and Instagram?
Habits form when not doing something causes pain.
For every aspect of your business, you need to move from pleasure seeking benefits to pain alleviating benefits.
Jay is on point about how to create habits. You do it with a consistent hook. Connect a user with a solution to his problem enough times with consistency, and it becomes a habit.
There are four parts to a hook:
Triggers are the first step in the process a user takes to alleviate his pain. This could be call to actions, emails they receive from you, etc. You have to tap into people's emotions in order for triggers to work.
Emotions that trigger the most actions are: Dissatisfaction, lost, bored, lonesome, confused, frustrated, discouraged.
Some examples of triggers and the apps we use as a result:
Find your emotional trigger.
Every time my customer _____, they use __my_app__.
Going back to the painkillers analogy, the app's actions should alleviate pain, fear, or rejection.
Remove as much friction as possible for users to complete these core actions.
Action must lead to a reward (step 3 below). Here are some examples of actions that reward us on popular apps:
Figure out your core actions.
It's this step that most startups screw up that results in apps that don't get engagement.
You need to carefully plan rewards for each action a user takes.
Rewards release dopamine in your brain, which leads to addiction (habit forming technology).
It helps to imagine your users as mice. You have to keep rewarding them for the right actions to make them want to go through the maze each day.
Some social rewards that we all seek (consciously or subconsciously):
Rewards must solve the pain.
Don't just give a reward for the sake of it. It must solve their pain. That's what they came to your app to begin with.
Predictability of rewards does have diminishing returns. As rewards become predictable, they become less interesting over the long haul.
So you need to have some variable rewards that are not consistent each time the action is taken.
When a user invests in your app, it makes it hard for them to abandon "their work".
The investment could be: time, money, personal data, social contacts, content contributions.
Right from when they first start using your app, they need to start investing in it. Keep it small at first so you don't scare them away with too much work.
I hope this gives you a conceptual canvas to start designing your app's experience.
Remember, build a painkiller, not a vitamin.