I've been role-playing for 26 years. I received an old version of Dungeons and Dragons for my 12th birthday, didn't read it, and it wound up on a bookshelf for a few months, until a friend convinced me to give it a try again. He ran me through my first dungeon, and I learned a little bit about the game that way.
Within a year (was it even that long?) we were using Advanced Dungeons and Dragons (Deities and Demigods had just been released) - but a bigger influence came upon my gaming style as GM and player than any game product would: MTV. It burst on the scene that summer, and we played RPGs with MTV playing in the background. The early videos - those that weren't straight up performance bits - influenced all of us (especially me) and made rock & roll an important part of my gaming style ever since then.
Time passed. We tried different games - Traveller, Call of Cthulhu (which was brand new), Gamma World, Top Secret - but it was all the same. We also gave a shot at the 1st edition of Villains and Vigilantes, and later the 1st edition of Champions.
The latter was our first encounter with 'built' character systems. And it wasn't that bad, at first.
So those latter two games became staples for friends of mine and I for about two years. One campaign in High School, a Champions game, came to an end after half of our team turned on the other half and arrested them to avoid prosecution for criminal activities. (The GM was really serious about the law, and too many of us became 'casual killers.') The drama this led to in game really impacted me. (The out of game drama - while considerably less - did lose one friend from the group.)
The next big influence on gaming came to me in college - in the form of a GM who had, apparently, issues with females role-playing. While I'm a male, I couldn't take his blatant misogyny, and neither could anyone else at the table. (I won't burden people with the story here - it was ugly.) The last night of that game ended with all four players standing up, one of us comforting the distraught female player, and another telling the GM in a very serious tone that he needed to seek psychiatric help.
I didn't game much for a few years after that. I'd work on games, but I never really played or ran them.
But then I got my hands on Warhammer Fantasy Role-Play - and I think it was the completeness of the world that sold me on the game. Make no mistake about it - the rules were (and still are) awkward and clumsy, but the world lived and breathed. That and the beautiful art. I ran a game for a few months, eventually having to quit for real life issues.
Those issues led me to move half way across the country - from Illinois to California. I didn't game for about a year and a half, but then I wound up speaking to a young woman who convinced me to start an AD&D 2nd Edition game. (This was the last AD&D game I ran.) The game was a blast - and oddly enough, most of the players were female. This led to me having to run a game in a way I never had before, but I found it really refreshing and enjoyable. (When the only reward offered for one adventure was a favor from the local Duke, I was surprised when one player later told me it was the best treasure she had ever received.)
That game eventually morphed and changed and gained players and lost players. One big step for me was creating a setting idea where some of the characters were Vampires. In Chicago. I ran this using the Hero System. Boy, was I shocked and surprised when Vampire: The Masquerade came out. (Especially with Chicago by Night being one of its first supplements.)
Well, when it did come out, that was it.
I had played a lot of games before then, but for some reason, the general idea clicked with me. I'll admit I didn't quite get it at first (the original games I ran were pretty much "blood-drinking superheroes who the sun hurt"), but that didn't matter, because as more games came out for the system, the more I found I liked.
These days, I'm running the new World of Darkness a lot, and am about to take my first step in entirely redesigning the setting. I've read more games that have had a positive impact on what I want - especially some of the more indie games out there - and I've tried my hand at writing my own game. (The most successful of which was something I co-wrote with a friend many years ago - a game called Storyboard, that maybe people here have played.) I keep looking for new influences.
My style has evolved to this:
* I want good characterization - if you're just a bunch of stats, forget it.
* I like things to start bleak. Give the characters a chance to make the world better.
* Dark doesn't necessarily mean angsty. (I've never had an angsty Vampire character. Ever.)
* Players who don't get a chance to kick back in character eventually snap.
Hope that wasn't too dull for people.