I think the thread title and the questions in the OP are not the same, so I'll answer both.
Yes, my tastes do change, both in the short and long term. In the short term, I sometimes get a bit burned out on a given system, or get really excited about playing a game (based on word of mouth about the game, a book or movie with a similar feel, or the like). In the long term, my tastes have changed, although the core is still basically the same. When I was younger, I had a lot more time and enjoyed fiddling around with rules systems, world background, and the like. Now, I am busier, and prefer to make only minor changes to rules, and to spend more time focusing on things that show up in play, and prefer to avoid detailed background that will not affect play (detailed background that the players can discover or that informs NPC actions and plots are still important, of course).
I like a wide variety in my games. I enjoy playing different game systems and finding their strengths and weaknesses. I also like to play with a system that strongly supports the kind of game I plan to run. As far as genre, I generally prefer heroic fantasy, space opera, urban occult, and street level or slightly higher superhero games, although I am open to games outside of those genres. I have been playing and running a lot of 4e lately, and I've been jonesing to play or run something different for awhile, and I'm excited to be playing in a Wild Talents game starting up soon.