It could be something about the way they sound, look, aspect of their personality etc.
Don't say everything! Bah lol pick something
For Baekhyun, it's his unique and warm vocal tone. He has my fave tone in all kpop. I especially love it in ballads and rnb songs. He's the king of those. His voice makes me melt. Even in Exo, a group of beautiful vocals, his stand out to me so much.
For Kihyun, it's how his love of singing is so apparent in his vocals. It's like the sound bursts out of him, almost like he can't help it. He has to sing. His facial expressions and body movement show it too. He was born to sing.
Wby?