A guild and a raid are not always the same thing, and the skill set required to lead one does not apply to the other.
You're upset because of several factors.
1. You're not raiding with people in your guild. However, even with as many people in the guild, how many of them want to raid or aren't already in one of their own. Is your guild even a raiding guild? (I have 2 people in my guild. Yes, I raid with all 1 of them.)
2. The quality of people you are raiding with are below your standards. What are the standards? Perhaps the standards are simply lower and you are on the high end of the spectrum. It's not uncommon for people to find themselves better geared or skilled than the people they group with, in every group there must be a numerical best (though judging by things like meters alone is never a good decision). This often leads to a sense of wanting a better group because you are the "best" and no one else measures up.
As for whether or not you should leave your guild, that is a decision for yourself to make. Maybe you should just lead a raid yourself, there is nothing in the rulebook that says a guild leader has to be a raid leader.
"In anything, if you want to go from just a beginner to a pro, you need a montage." /w TankSpot WTB Montage for Raiders.