Usually the RPG is the best (for me), solely because you know it will have more complexity and story behind the game. You can put in hours of gameplay into it and never get bored because you are being set forth into a story, except in modern cases, you determine how the story will turn out!
The only downside is, once you beat it, there is hardly any replay value left, unlike the shooters and the puzzle/skill games where you can play much of the same thing and still have fun doing so. So if there is an RPG that can remedy this completely, it will be the sole best category out there.
My favorites are adventure, skill, shooting and strategy.
In order:
1.Adventure-I am just an adventure person. 2.Strategy-I like Colony, Warfare, Age of War, Warlords, and Gemcraft 3.Shooting-Just because of Raze 4.Skill-I like figuring out puzzles. It can frustrate my brain. But it's fun. =P
Overall, I have a heavy preference towards strategy and action, with strategy somewhat ahead of the other. This counts with flash games and other games in general.
Definitely Strategy, and Adventure depending on how the creators categorized their games. Strategy games (mainly RPGs and RTSes) just appeal to me the most. Basically, I'm just a huge Krin fan, as well as Final Fantasy and StarCraft