Theres a guy I known for 2 years, been off and on dating him, he's sweet kind and caring?

Why am I not into him? He is 25 , has a great engineer job, drives a nice car, has ambition, motivation and good credit. He is a decent looking guy. He has wined me and dined me, and taken me nice places and he is a good guy and very pive. The only thing is, there is no spark. Like when I kiss him I dont feel anything. Like Im kisssing my brother. Why do I feel this way? He is a good guy and a great candidate for marriage. I am pursuing a nursing career and im 25 so I am thinking futuristic. Should I overlook the spark and continue to date him , or should I just let him go and be friends? I have known him for 2 years but have been dating him off and on because I still believe that one day we will create the spark.