What is "¿Quieres ser mi novio?" in English?
Again we get to politeness and in Spanish it matters. preferably you would quieras or querría, i.e. subjunctive or conditional. If you were putting it to him as an ultimatum then quieres, e.g. do you want to be my boyfriend, or not? The romance languages are still big on politeness and these two forms are ways to practice it. It's a little bit there in english with will or would. good luck with learning this beautiful language.