You're in for a couple weeks' worth of these. But if you want a quick summary of me as a GM or player, this is probably it.
LIKE: THE CHARACTERS
The most fun in a roleplaying game comes from playing a role. I like pretending. I like getting to do cool imaginary stuff when I'm playing. When I'm GMing, I like to let my players do cool imaginary stuff. In both cases, I like it when characters are trying to achieve goals and then experience surprising events. I like making characters just as a pastime. Characters should both drive a game's action and be the focus of that action. Not the environment, not the story, not the GM's plans - the characters.
Characters should also drive story design. I agree with Robin Laws, who has said that a person's character is their expression of what kind of game they wish to play. A good GM looks at what the PCs are like, then creates/tailors sessions to fit what those characters do. A fantasy party of Fighter, Mage, Cleric, Thief should be involved in much different situations than Bard, Mage-Thief, Monk, Fighter Who Specializes In Ranged Weapons. Those two sets of characters represent different sets of expectations, individually and collectively, and that should drive everything else that happens in the game.
I love characters.
DISLIKE: DESCRIBING ENVIRONMENTS
This is one of my biggest weak points as a GM. I don't much care what the environment looks like, what's in it, etc. After I toss off a quick description to set the scene, I'm done. The environment is a backdrop to me - it provides a little flavor, but it's not designed to be an integral part of the action. I don't want to tell you how many tables are at the inn, or what you find hanging on the wall of the smithy, or the contents of the ship's hold. I just don't care.
Same goes for when I'm playing. I don't really want to interact with the environment in lots of nifty, thoughtful ways. The space around me isn't what's interesting, be it a room or a cavern or a giant singing tree - it's just a physical boundary inside of which interesting things can happen. Perhaps it's because I don't visualize well. I really don't - I'm almost completely unable to picture things in my head. So I don't want to do it, regardless of which side of the GM screen I'm on, and I don't enjoy adventures that require it.