Beyonce and Adele by far. First of all they both sound amazing live. And that makes for a great singer. Adele's voice is very unique. Beyonce voice is amazingly beautiful. beyonce has been around for years from destiny's child too now.
I'd say Taylor Swift. Her not so famous songs are beautiful. Her self titles album is my favorite and the one with Beautiful Eyes. Taylor is my go-to singer after a bad day, and she is for lots of girls (: