I have a high preference to games of skill over games of chance. Most of the fun I get out of video games is in understanding the patterns and behaviour of the game world, and then using that understand to master the environment. For this to work, the game needs to be fairly deterministic in nature.

It's interesting that when tried World of Warcraft, I lost interest quickly as I found it too much like a slot machine.

I don't know if it's a personality trait (I'm a programmer so I tend to analyze everything) or because I grew up in the era of 8/16-bit games, where games were a lot more skill based in nature.