Hmmm....ok. Im going to try and give you a few ideas from a womans point of view. Mostly because I see this question "pop up" (small joke) over and over again on these marriage sites. Im 37, been with my husband for 19 years and have 2 kids. So you understand where my perspective comes from.
1. The majority of women don't put as much importance on sex as men do. Most men associate sex with love and caring. Women show they care for you in other ways, so there becomes a misunderstanding. She picked up your dry cleaning, cooked your favorite dinner and entertained the kids so you could watch the football game (this was the effort she put in to show you that she cares). After all that she was tired and didn't want to have sex. So you interpreted it as her not caring for you. You had a need and she failed to see it and comply. Now you are mad. SHe is mad because she did show she cares and you didn't acknowledge it. Do you see the misunderstanding???
2. Is the lack of sex the only problem in your marriage. If not...if their is turmoil or unresolved issues in the marriage, you will need to tackle these before trying to improve your sexual relationship. Women don't want to have relations with people they are angry with.
3. Realistically look at the situation. Do you have young kids? Toddlers are a kill zone for sex. After being mauled all day. After hugs, kisses, boogers, peanut butter on your pants, piggy back rides and packing children...the last thing a woman wants at the end of the day is to be touched. She wants 30 minutes to herself. Sorry. Which brings me to my next sex killer...privacy. Do you actually have 30 minutes in your day alone with her??? And I don't mean at 11 o clock at night when the kids finally fall asleep. 3rd issue...health issues. You didn't outline any specifics about your situation, so any depression, anxiety, ect.... That's a different problem all together and you might want to research any health issues so you can see what your spouse is dealing with and how it affects sexual relationships.
4. Warning....You will have to put away your male ego away for this one. Is she enjoying sex. Does she get satisfied. Because frankly...if I have to choose between 5 minutes with my husband where I will receive no satisfaction...or doing the dishes. Im a busy woman... at least my kitchen will be clean. I'm making light of the situation...but it is serious. think about your sexual relationship...are you giving as much pleasure as your getting?? If you suspect your not...you may want to do some research. Google has many great ideas. And step by step techniques for success.
5. Try something new...I recommend sexting. Start slow, some flirting and sexual innuendo over a lunch hour. Then if she seems interested, build up from there. If she is reserved, it might give her the chance to loosen up a bit. Maybe reveal what she IS into. But ultimately, the goal is to get her mind on it. Thinking about it, wanting it. (if you don't know how to sext, that's right...google)
6. The vanilla comment...I'll avoid this one.
7. This is going to be a shocker for you....if you haven't had sex since Valentines....YOU ARE NOT the only one sexually unsatisfied in your marriage. SHE IS TOO.

So..I didn't answer your question. Should you stay or should you go? Obviously only you can answer that. Hopefully my ideas or suggestions gave you something to think about.
I know I lightened up the topic a bit in this post, but seriously. 10 years ago I would have thought...Your going to throw away a marriage over sex??? Now, I do understand. It can turn into a major issue in the marriage, because it is obviously important to you. If you are happy in the other areas of your marriage, I hope you can find a middle ground. Wishing you the best.