Not every great song makes a great ringtone. Keep these tips in mind:
Ensure the audio isn't distorted or too "bassy," which can sound crackly on small phone speakers. new_ringtone_english_song_ringtone_bgm_ringtone...
You’ll typically need to use the GarageBand app method or iTunes to convert a song into a .m4r file to see it in your Ringtone list. Not every great song makes a great ringtone