Theme is an interesting aspect to games; more often than not, they are the make-or-break factor that will determine its success. I also have a slightly unique perspective on this, as I personally enjoy theme less than most.
Firstly, let's define theme. In its broadest sense, it is anything that makes the game immersive. Themes can be tacked on, or core to the game. Take Super Mario Chess for example. The game itself is no different from regular chess, however, they are marketing it on the hope that involving Mario will generate more sales. That is a tacked-on theme. Something like Twilight Struggle has theme at its core; it starts at the core and builds outwards. Everything about that game is based on the cold war, including all of its mechanics and content. There are also mixed cases, such as Carcassonne, which could just as easily be about building a dungeon as a city, or could just as easily be an abstract control-the-colours game.
Closely tied in with Theme is Art. It is easy to underestimate the importance of having good art. I was genuinely surprised for most of my Magic playing career, how many people got into it because of the art. It was something I generally didn't care about or even notice, and yet it is a major drawing factor for many of its players (no pun intended).
Art is the bridge between the every-man and the game. It is very difficult to appreciate abstract games without playing them and having an understanding of it. It is easy to appreciate something relatable; Warhammer thrives on this concept. While it could very well be an abstract strategy game, it instead takes place in a very engaging universe filled with interesting characters and stories, that ultimately have very little to do with the actual gameplay. I admit to have started playing Warhammer without any prior knowledge of it, instead just basing the decision purely on its aesthetics.
Unless you are talking about a video game (or Last Night on Earth), music is not a factor. That being said, I find that sound is far more important than graphics for creating immersion. Music is good, but sound effects and voices are far more important.
ridiculously amazing soundtrack, and exceptionally good voice acting. Dungeon Keeper 2 is a very old game, with terrible graphics by modern standards, however I find it easy to get into because of the beautifully done voice acting and sound effects.
I also want to make note of the original Fear game; for most of it, a very annoying high-pitched sound is constantly emitted. It is fairly easy to ignore after a minute, but it does keep you from getting psychologically
Depending on the game, there may be a universe associated with it. I mentioned the Warhammer universe, which guides the game without directly affecting it. Having relatable stories and characters (or a franchise) associated with your game is often a boon, and indeed the sole saving grace of most shovelware. It becomes more engaging to pit Eddard Stark against Joffrey Baratheon when you know the backstories of those characters.
Theme is an important aspect of gaming, as it helps to draw in players and make the game more engaging. More is generally better than less, so long as you are not just tacking it on. Fluff is great to have, but not essential. It can also occasionally make things easier to explain as well, if your mechanics are tied into your theme, as everyone has an intuitive understanding of such things as gold.
Until next time,