Some of the most fun games are based on an idea and feeling a director wants to get across rather than a genre. Games like this feel original and fresh in a world where all else can be classified as RPG, Shooter, or the like. I like when games are so unique that you have to describe them by what you do in it rather than naming a genre. Sony's Tokyo Jungle is a recent example of this.
In Tokyo Jungle you play as an animal (first a domestic pet, but more exotic creatures are unlockable) and set out into a post-apocalyptic world void of human life and fight for your survival. All the animals are extremely savage and feral and just about anything can kill anything else with enough skill. It's hard to pin a genre on it because there really are none that describe it.
It's not an adventure game because the world is pretty small overall and pretty straightforward (i.e. don't die). It's not really an RPG but you do fill up a hunger gauge and eat creatures to gather kCals and rank up up to 2 times. It's not an action, stealth, or fighting game because the fights are dynamic and often short. It's a survival game if you want to put it in one word.
The game doesn't start with a genre and fill in the traditional mechanics, it starts with an idea (animals fighting for survival in a city) and takes useful elements of games as a whole to make something that fits well with the concept.
I normally don't buy video games at all, even cheap ones, often waiting for holidays or any extra income before carefully choosing something that will keep me entertained and show me something new for a long period of time. But as soon as I saw 3 minutes of gameplay on YouTube, I knew I had to have it. Now.
I fired up my PS3 and downloaded the full game as fast as I could, possessed by the curiosity and excitement of finding a new game. Something different. Something I could learn from. Those types of games are my favorites. Honestly, how many other games let you control a pack of Pomeranians and take down an Elephant?
I really just wanted to talk about Tokyo Jungle because I like it when games are unique like this and I really wish more games could surprise me this way. There's just always something magical about the good ol' arcade days where there where no genres and games were just games, each being unique or a sequel. I kind of see that coming again with the smartphone app market, but maybe we're still transitioning into something better.