You posted in the right place. The best way to find out what makes up a good single player mission is to check out some of the high quality missions in the mission depot. If you want a list of what generally makes up a good quality mission, then here's one:
- Overview that draws the player in, good image (an in-game image is best) and enough info that doesn't give the plot away but enough that entices the player to play the mission.
- The intro is very important in conveying the mission plot. Good quality intros take a long time to make (very complicated process). Most 'good' intros I've seen in the past have been quite awkward to watch, because of wrong camera angles or text that isn't on the screen long enough etc. The intro is probably the second most important aspect of a mission (at least imo).
- It's quite difficult to say what makes up a good quality 'mission', because everyone has their own tastes. I could say that lone wolf missions are really good and yet someone else could say that lone wolf missions are boring and pointless. But, in general, for a good mission you need a solid plot, complex scripting, loads of special features (dialogs, voice acting, in-game camera etc). The plot is the most important because it is that that keeps the player entertained.
All of this is subjective. What makes a good mission in my eyes is going to be different to how someone else sees a good mission. So, like I said, it's quite difficult to list what makes the actual mission itself high quality.
- An outro that ties off the plot, using complex camera scripting. The outro should give the player a sense of accomplishment. You don't want to have spent so long on a mission, only to end up seeing only a 'mission completed' message. The outro should be similar to the intro in terms of quality.
- Briefing (forgot to mention it). The briefing should be comprehensive, clear and without digress. All information should be conveyed clearly, with objectives outlined. The briefing should furnish the player with all the necessary information he will need. Most mission makers will try to put as much info into the briefing as possible, some of it unnecessary. I've fallen into that trap a couple of times. Whilst you don't want to put too much info in, you don't want to have the player enter the mission clueless as to what to do.
That's pretty much what I think makes a good mission. It is subjective, and I'm sure someone will have a different opinion to me on this. But, I think that there is one thing that we can all agree on about what makes a good mission: a solid, entertaining, enthralling plot.
Like I said at the start, check out some of the missions in the mission depot.
Hope this helps
Gruntage