Ha! I just said I hate picking favorites when it comes to Chopin, and here I go voting again.
I picked the 4th Ballade because I only recently fell in love with it - within the last year. I was raised listening to the 1st and the 3rd Ballades, and I love both of them (though the 1st more), and I was introduced to the 2nd Ballade in high school, and fell in love with it, too.
I'm not sure what had turned me off about the 4th Ballade before...I think it was perhaps the simplicity of the opening 7 bars, though it sounds stupid to say it now. The main theme is beautiful, and more beautiful in each of its variations...and when the theme of the opening 7 bars comes back in the middle, it's downright profound.
Anyway, I love all of the pieces on that list. I wouldn't say that the 2nd Impromptu is my favorite Impromptu, but I am familiar with it. If it's for solo piano by Chopin, I am familiar with it - and the Concertos, too...but sadly, I don't have recordings of the Concertos. I had them once, but I don't know what happened to them, and I don't have them on my computer. I have recordings of all the solo works, though, including the posthumous ones.