In general, do you find yourself more attracted to people with similar or different interests, life experiences, political beliefs, and religious backgrounds? Do you think having some common interests/goals is essential for a successful relationship?
Religious beliefs has to be the same. No excuses there. No other discrepancy, other than incompatible genders or sexual orientations of course, will cause more stress in a relationship or subsequent marriage.
Other than that, however? I am of the belief that opposites attract, but only within certain tolerances. Polar extremes will not mesh at all, as there is no common ground. The most extreme hardcore punk rocker would hardly be able to communicate with a sheltered, timid church mouse. Someone so adventurous they always want to be out and be active, if not be risking their lives rock climbing or hang gliding, would be as weighted down with a homebody as this laid-back individual would be in a constant state of stressful anxiety from being pushed so far out of their comfort zone. Meanwhile the homebody will only bore the thrillseeker to madness. Such comedic pairings only work in fiction.
However, in general opposites do attract because what is strange and mysterious is also fascinating. No one wants to be with someone just like themselves; most people, deep down, do not like themselves or at least dislike a good many of their own character flaws. If your mate knows nothing different, does nothing different, and brings nothing different to the table, then it's hardly much of a relationship at all. There are no new experiences. Nothing new to learn about the other person. All that can be said here is that you get to have sex, but one could debate that since it's a constant struggle to keep things exciting in a relationship, this aspect shall soon suffer as well.
For me, personally, I'm a very serious and hard-working individual. After work for the most part I'm rather laid back, and when I do go out I usually stick to my usual haunts. I deal with stress well, and while I'm the pillar of strength for so many people I'm able to do so by taking so many burdens upon myself. I hold it all inside, and carry my emotional pain until it wears me out. I worry and I brood.
In my case, I need a girl who's fun and carefree. I'm a good provider and take pride in protecting those I care about, so she can be weak and frail, needy and dependent by contrast. But she needs to be sweet and caring, compassionate and able to tend to my emotional needs that I so blatantly neglect even as I provide for those physical and financial ones in much the same way. I take charge and am highly organized; I need someone more easygoing and spontaneous to bring balance to the pairing. I'm far too independent for someone to try and boss me around, but at times when I'm stuck in a rut I may need gentle urgings to sweet-talk me into doing the things that in the long run would be best for me, even if it's simply going out when I'm content enough to spend the evening in my recliner. Though dissimilar, I still would prefer a few common interests - hobbies, similar tastes and the like - but that's not the main thing as much as it'd be nice to have a few things we could share and enjoy together.
Perhaps the best example I could give is one that is pathetically geeky, but it is not unlike the serious, brooding fighter and the cute schoolgirl who befriends him in virtually every Anime series. But so far, there is no Kagome for this Inuyasha. There is no Tohru Honda for this Kyo. There may never be.
I wish I had an angel, for one moment of love...