OK, so here's the thing. I used to be really into the question of "What rules to use?"
You know: "What system to use?", "What houserules to use?"
And I still am pretty opinionated on the topic(probably a bit more that I should be). But it hit me recently, that, while rules may be important, there is something more important: Content. What you run and how you run it.
Because rules can RUIN a game, creating a distraction, taking the focus away from the actual role playing experience. But it's rare that the rules make a game session GREAT. That's more of a question of the adventure you're running and the art of how you're running it.
And it's an easy mistake to make, focussing too much on the rules, at the expense of content. The rules are static, mathematical, open to easy analysis, relevant from session to session. This, as opposed to the adventure you run, which is always changing, or how you're running it, which is a dynamic, inconsistent process, for which there is no definitive guide.
I look at the incredible bounty of Rule Systems our hobby has created: there are so many RPG systems and variants out there. There may well be more systems and variants than there are adventures/modules. It makes me think that I'm not the only one who has made the mistake of over-emphasizing rules when I should have been focusing my best efforts on Content...