There are a couple of elements to this.
1. You want your screenshots for your game to be as good as you can make them. Most people only see a few screenshots before making a decision on buying the game, be them on the back of a box on a web page in a review. So you really want them to be as good as you can make them.... (they will Never be perfect!).
2. Screenshots highlight a section of your game, or level or scene or whatever it is. This highlight does not always show context. It is unlikely to show as well as if the level is scrolling, moving etc. This highlighting can be a bit of a shock to view. It will tend to be plain. And we don't want plain in our pictures. #1 has already stated how important they can be.
OK, so you can alleviate some of the screenshot stress by only putting the ones you like into your press pack etc. Simple...
There is another great use of screenshots that most people do not bother with, or have the time to use them for. I am talking about Sprucing up the area of the screenshot. Giving the area a nice working over to improve the look, and even perhaps make an average screenshot look good enough for the press kit.
I have just done this to a very limited extent to show Leilani how this works and how beneficial it can be. So I took several screenshots, then one lunch time we sat down and discussed what we liked and didn't like about them. Good fun and the food was great too! (Thanks Brick Oven).
- The Sky is missing something, it is too bland.
- The trees look all the same color wise.
- The front log is a bit over bright.
- The shadows under the trees is a bit small, and is over the roots.
- The area does not look dark enough for a forest.
- I placed some clouds in the sky, it was easy to pull them from another scene and place them.
- I used to have a routine that gave the trees a variety of color. This was broken by me in the prefab. I actually moved the re-colorizing code to another class. So that was an easy fix.
- Easy to darken the front log of course.
- I spent most of my time working on the shadows for the trees. I had to get a good angle and also a good size for the trees. Now I think it worked out great, only I do believe I will darken under the trees a bit more, but the lengthy shadow is good.
- With the extending the shadows for the trees it addressed the darkness of the forested area quite well.
I hope you like the example above. I now believe that this screenshot is much better than the first and also good enough for the press pack!
Good luck fixing up your game :)