Nah, it's not surprising that most people who claim this so called 'spark' is the defining factor have been in failed relationships.The spark thing is just a superficial idea, but let me really explain what it is. Its an initial interest in someone. When you first meet someone, you have no idea who that person really is or how compatible you will be with them. You have no real feelings for them because you don't know them, you are only capable of having a strong 'interest' in getting to know them at this point. This initial interest is just based on things like attractiveness, percieved personality etc. People mistakenly think this idea of a 'spark' is what forms a relationship or keeps it alive or makes people love each other but thats not true. That's why its called a 'spark', it's meant to be short and fleeting. Its just an initial interest that may cause you to pursue a person in the first place. Think of it like starting your car, when you first turn on the ignition. Its a short one-off event to get you started, and then it's things like how compatible you are and how you love each other, companionship etc that determines if the person is 'the one'. sparks can definitely occur with someone you've been friends with or known for a long time. You might suddenly begin to see them differently as you learn more about them and feel like you want to get to know this person in a new light.That's why i think the best relationships are built on friendship/companionship. In my opinion a successful relationship = love + companionship. I dated someone for a long time. I really loved this person but discovered the hard way that there really was no companionship. When we took away the 'love' and intimacy aspect, we discovered we weren't truly friends. we didnt have a lot in common, we didn't have much to talk about if it wasn't related to being a couple. we just weren't really 'companions'. we couldnt just go out on adventures together and talk as friends and interact as companions. We were together 3 years. it sucked, but i realised the relationship would never work so I ended. When you meet and love someone who's also true friend/companion, it's the best feeling in the world.
Everyone is different. If you're the kind of person who's soley interested in casual dating (and that's perfectly valid) then those inititial superficial sparks can be enough for you because the relationship (if you can call it that) isn't meant to last. but if you're who's looking to find 'the one', focus more on finding a companion.