so many choices... I don't think I can force myself down to one, but here some of my favorites:
Blue - Joni Mitchell
California, River, and Case of You are 3 of my favorite songs. I could barely even care about the other tracks, which are good in any case, and it'd still make my list. Joni Mitchell is simply one of the most talented songwriters and musicians to ever exist. Definitely the best as a combination of the two skillsets. And Blue, imo, is her at her best.
Back to Black - Amy Winehouse
... except for the part where the US edition had these abysmal hip-hop remix bonus tracks at the end. But all the regular stuff is fucking fantastic. I can think of very few singers who sing with more intention than Amy did. I would say that it's criminal that this didn't win album of the year in 2008, but I can't fault Herbie Hancock doing a Joni Mitchell tribute album, seeing as how much I love Joni (see above).
The Blessed Unrest - Sara Bareilles
Every song on this album is perfect for my tastes. It has flawless and sincere vocals presenting interesting, at times masterful, lyrics all wrapped up in skillful, but definitely not overdone, production. It's almost like a modern, much more poppy version of Joni Mitchell (wow I really can't stop talking about her).
Whokill - Tune-Yards
Now for something not at all related to Joni Mitchell! This album is so bizarre and yet so perfect. I think it says an awful lot that it won best album in the Pazz and Jop poll in 2011, when that poll overwhelmingly tends to pick blockbuster hip-hop albums (since 2000, it has voted for Kanye 4 times, for example), beating out a Kanye/Jay-Z collab... all while only selling ~47,000 units that year. You don't even need to follow lyrics to enjoy the experience due to powerful rhythms and a voice that demands attention, but if you do like lyrics, it's got power there too. The lyrics speak of violence and inequality in a cynical yet curious way that could only be accomplished by someone who sees themselves as an outsider within their own culture. Almost like the lyrical commentary of a certain miss Joni Mitchell (goddamnit).
tl;dr everything is Joni Mitchell