Céline: Power of Love (came before MHWGO and made her a mega superstar)
Mariah: Vision of Love (but I agree with Hero as well)
Whitney: I Will Always Love You
Shania: You're still the one (worldwide)
Adele: Rolling in the deep
Shouldn't Cher's signature song be If I Could Turn Back Time? I know Believe was her biggest commercial success, but it came so late in her career it just sounds weird to me. IICTBT is still remembered to this day.
I would say Cher's is Believe, as Celine's is most likely MHWGO. That's what they're most known for.
