Within the different genres there are many variables and considerations that need to be taken into account. For example multiplayer first-person shooters require a great deal of thought going into the likely conflict points, whether team based, duel or all-on-all. Singleplayer story based games require a lot more focus on implicitly telling the story without being too in your face about things. All level design has to be intuitive and the ease of completion needs to be judged carefully, obviously you don't want the maze to be too easy for these pesky mice/gamers but you also don't want people to stop playing because they're unable to work it out.
One person who has shown their understanding of this particular subject, whether purposefully or accidentally, is David Johnston. He is the original designer of de_dust and de_dust2, for those of you who don't know, de_dust was the most played maps in the world at one point. I would personally say that it has significantly changed gaming history, I know I spent far too long wandering around those particular mazes. They were made for the 4th beta of the Half-Life mod Counter-Strike back in 1999 and were kept in for the final released mod and then kept in for Valve's release, and then made again for Counter-Strike: Source in 2004 and made again for Counter-Strike: Global Offensive in 2012. The Counter-Strike games have been some of the most successful and longstanding games in the PC gaming and esports environment with the original Counter-Strike still being played in some tournaments today. De_dust and De_dust2 are the staple maps in the series, they are played by virtually everybody who plays the game. Now that I've got that off my chest back to level design and David Johnston. I said "purposefully or accidentally" because although it is clear that he really knows what he's doing now, he was around 16 or 17 when he made de_dust.
|Level Plan of de_dust from Counter-Strike 1.6|
You can read about the making of dust here where he explains that he had previously had "little pre-planning" when making maps and the same was true for de_dust. After reading through the page it is clear to me that there is one main thing that helped him make some incredibly successful maps is that he thought about what he was doing, isn't that simple? In all seriousness if you put your mind to something and just think about how people will perceive it and how you want to affect that perception it seems you can do a great deal by just thinking. In this case he thought about how the terrorists and counter terrorists would play, what the fastest routes would be, where the sniper nests would be, how to make things fair for both sides... he though about everything. And he solved issues as he found them. He used common sense as he puts it. Here he has written a really good article on common sense as a designer.
Environment art and level design often get confused. Orange and grey maps which are used by Valve to test how well a level works without confusion or distraction show the clear difference between level design and environment art. These have been adopted by the modding community for Counter-Strike Source and as you can see below these maps are very interesting, and they are definitely gameplay focused. That is the point of multiplayer FPSs, they are about gameplay, they are essentially sports and so the visuals are extra, they are nice but they add to the gameplay.
|Level available here http://maps.cs-bg.info/maps/css/1667/|