I have a strong preference toward games with simple rulesets and deep gameplay. I generally like a minimum of randomness in games, and detest games in which superior play can be routinely bested by bad luck. While artwork can be important to me, theme is virtually irrelevant to me unless it aids in understanding the gameplay.
I'm an ardent proponent of game systems (Icehouse, Decktet, Playing Cards, PiecePack...) and yet still find my pile of German cardboard steadily grows.
I strictly follow BGG's rating rubric with my ratings. This means that some games that I really enjoy and think are great games get deceptively low ratings because I'm not always up for a game of them. BGG Secret Santa:
Thank you, Santa!