One of the reasons why there are so many different online slots, compared to other types of online casino games, is that there's so much flexibility when it comes to the types of themes used in the games. You can literally take any game out there and change the graphics to suit just about any concept that you want, but it's the way that the theme comes together with the features, soundtrack and other aspects of gameplay that really create the overall experience.
To give an idea of how important it is that everything comes together, we're going to give you an example of a game from around 2004-2005. We won't name this title or the software company that created it, but it suffices to say that it was based on a major movie franchise that was one of the highest-earning film franchises of all time. The software company who got the rights to the game thought that having a slot themed after this series of movies would be enough to carry it, and they didn't really put much effort into making sure that this theme fit the rest of the gameplay experience.
Guess how that worked out for them? People played the game a lot in the first couple of weeks that it was released just because it was something new and had a big brand name attached to it. However, the gameplay itself was well below average, and it quickly fell in popularity once people realized it was all flash and no substance. This is the problem with relying just on the theme of a game: Without great features and payouts that make sense in the context of that theme, its popularity will not last.
Every type of branded media you can think of has been used as themes for online slots. This includes magazines, films, television shows, comic books, video games, bands and tons more. The whole idea behind this approach is that these forms of media will already have a bit of a following behind them, so by getting a licensing deal to create an online slot based around these themes, you leverage that popularity through the existing fan base.
However, not all successful slots require a pre-existing brand as a theme. In fact, many of the most popular games released in the genre have been based around somewhat generic themes like Greek mythology, Norse mythology, cops and robbers, romantic scenarios and other general setups for stories. In these situations, it's the graphics, gameplay, soundtrack and feature set that ultimately determine the success of the game. In fact, software companies can frequently create their own series of slots by developing their own "brand" for the games that players get behind based on gameplay alone. The Avalon and Thunderstruck series by Microgaming are good examples of this, as is the Jack Hammer series by Net Entertainment.
There are some themes that have been so popular that it seems like every software company out there has at least one game based on them. Egyptian themes are pretty popular, as are themes based on wealth. In fact, many of the largest progressive jackpot games out there today have a wealth-based theme. Online slots with themes based on animals tend to show up several times each year, as do games based on Asian themes.
What's ultimately the most important thing to take away from this is that picking a game based on a theme is fine, and there's nothing wrong with picking what looks interesting. However, if the gameplay of an online slot doesn't hold up, then it's not going to keep your interest for very long.