She has always been my favorite singer. I, like others have mentioned, do not care for her politics, but her singing has always been amazing.
She was a great singer before, but really took a risk when she started to work with Nelson Riddle. Turned out very successful, AND helped improve her already amazing voice/singing. She just kept getting better and better as she took on more projects, and more genres of music. Country, bluegrass, pop, rock, jazz, latin, opera ect ect.
I have heard lots of good female singers. But most had limited range vocally, or limited to one genre. Streisand, Ann Wilson, Ella, Reba, Aretha, Patsy Cline, Julie London etc are/were amazing. Not to mention Dolly and Emmy Lou, who she successfully "trio'd" with. But most limited to one genre.
Pretty amazing to look at some of the video's, like her appearances on Johnny Cash show in '60's, with Eagles in 70's, jazz in 80's. The video from her mid-70's Germany tour are amazing.
Certainly there are no current mainstream female vocalist showing that level of talent or range.