Like Corinna, a vignette is super helpful but I also think the biggest game changer when it comes to lighting, is adjusting the hues and saturation of your picture. If you add just a bit of warmth or coolness I think it really makes the whole picture come together and look more deliberate rather than a random snapshot out of your game. Compare these two images for example:
The unedited one is very neutral. The colors lean a bit more cool with the blue tones but otherwise it's generally neutral and doesn't really catch your eye. On the edited one, I adjusted the hues to have more orange and yellow tones and used an orange warming filter.
At the end of the day though, it really helps to have good in game lighting to begin with. Another example is these two unedited pictures.
I took the first picture when there was no sun and it was very overcast so the whole picture looks very blue, with the subject very yellow looking. Of course not every picture needs to have perfect golden hour/sunset lighting but try experimenting with different hues and colors. Just the slightest adjustment can really go a long way. Its also a good thing to remember that lighting isn't always black and white. I find that a picture looks much more believable if you choose light and dark values than complement the subject and the scene you are trying to portray.