The number one thing that the games I looked at (and others I've played personally) is that the game it's self is never one pure genre.; Each game is a mix of elements such as Mass Effect being a Acion/RPG or Metal Gear being a stealth based third-person shooter.
Other Sub Genres include:
- Hack 'n' Slash
- Isometric Platformers
- Survival Horror
That's just within the genre of 'Action-Adventure'. Many other games such as most Eastern RPGs all take place from the Third-Person perspective, meaning that it's just not action adventure games that take place from the third-perspective.
The question is though why are third-person perspective games so successful? In my personal opinion it's a mix of likablility from one aspect of the original game, eg: The characters or game play and peoples want to see more from that series and film envy. The latter factor is a pretty obviously answer but, I feel it's because of the point of perspective that helps establish these factors. This is because of the medium of film where in the view is but a watcher, where as in video games the veiwer is not only the watcher but also the controller and it's the player's input that progresses the story along. After watching many films it's a weird sense of finally having some control over your entertainment.
This is just my personal Musing though. Many video games develop strong fan bases either due to the strength of the character's personality or outward appearance, this results in fan works (such as art, fiction or even fan games) and even inspiration for people to work in the entertainment industry.
With this inmind since I'm not working on gameplay for my project I will be focusing on trying to make my two characters and their backstories as appealing/interesting to the audience. Next I will be looking at character archetypes to start to develop my characters from those base archetype models.