In terms of life experiences, I would say that falling in love with your dream girl and getting together with her would feel superior to speedballing although I cant thats happened to me. But life is about more than pleasure and that's all heroin and cocaine give you is pleasure. You're still aware of the fact that you're gonna come down and feel empty again and that knowledge puts a damper on the experience.
Other experiences I would rank above speedballing are spiritual/religious experiences where you feel true joy, because the promise of true joy is that it will not fade whereas all worldly pleasure fades. I have had some spiritual experiences on psychedelics which were totally ecstatic and felt as good as speedballing, making love to the absolute, because God is love and all goodness comes from God anyway. He is what you actually long for, not pleasure. And I don't mean to get all religious on you, I just know from many years of experience as a pleasure seeker than divine pleasures are superior to earthly ones. I will say that the feeling you get during the rush when you dont have much tolerance is heavenly. It even inspired me to seek God all the more, because if the feeling of being home, in God's kingdom is anything like that, then it is so unbelievably good that it is worth all the pain and suffering you could possibly go through on earth. Yeah, cocaine and heroin can make you feel like a god or heavenly being.