Donna Summer is one of the greatest singers of all time. she had a range that comes close to whitney's and revolutionized dance music by combining soul and disco and making ballad like dance music.
She literally created and Made an entire decade,Era,and Genre of music.
When it comes to vocals I have to disagree I don’t think her range was strong enough for Whitney’s but I agree she’s a really underrated performer and vocalist she had her own sound