Having similar interests is an important foundation for a relationship, after a while the passionate love becomes more sporadic at times and so it is important to have a strong friendship to fall back on.
The exchange of knowledge and passion will keep a relationship 'interesting' and 'worthwhile. Perhaps these terms seem flaccid and superficial ("I will only maintain a relationship if I get something out of it"), but ultimately, companionship functions better if both party's benefit from its dynamic; a simple truth.
Thus, Enjoying similar things is great. But symmetry is complemented by symbiosis.
My partner is incredibly passionate about immigration-related issues; Something I know little about. Over the years, I have come to appreciate the topic, and more importantly, have become more knowledgeable on the subject, simply by listening to her. A cheap and effective education; never a waist. Sometimes it bores the shit out of me though... but that's love; you put up with it to make the other person happy.
I really enjoy cringe-comedy stand-up performance, on which I am writing my Master's thesis. My partner HATES the feeling she gets from cringe-worthy moments (she hides in the closet
-LITERALLY- every five minutes while I'm watching "the office", or "peep-show" etc) but, she endures. Just so we can talk, and learn from one another. Gaining an insight into another human being is one of the greatest perks of a long lasting relationship.
However, have you considered the possibility that you might approach your 'guy', with regard to existential debate, in the wrong way? When trying to get someone interested in something you like, taking the approach from one's own perspective is no road to success. You'll have to empathise with HIM, and connect your interest to something he already likes. I enjoy a good philosophical debate as much as the next man and will admit that these can be rather 'aggressive' at times; its the nature of the sport to joust with you opponent. I learned this can be very intimidating to others, who do not share this hobby.
If it turns out that there is nothing you can do about his lack of interest in your passion, conciser whether this passion is more important than the relationship you have with your 'guy'. Is the answer yes, part ways, if no, then love him for who he is. This is essentially what you are asking of him; to love you for who you are, including your lust for the contemplation of the self and the universe you live in. But if he can't, or just won't, and you can't except that of him, then it would be hypocritical (and thus not serving to your best interest) to leave him; provided this particular 'lack' in compatibility is the ONLY reason you would want to.
1)Does he listen to you? Surprise you every so often? Think about you when you're not there? Laugh with you? Care about what you want/need sometimes?
2) Does he punch you every time you quote Hegel?
If yes to 1) and 'no' to 2); then you've struck gold in relationship terms as far as I'm concerned. If not, there's plenty of good men left in the world. And you could always try lesbianism, they seem to have a knack for existentialism.
* whether it is entirely immoral to punch those who quote Hegel remains ambiguous... but that's a different story.
