The original sold 6.27m on PS3 alone, according to VGC. And the Remastered version on PS4 sold 6.27m.
Not sure how much better this one will do, but I'll say 9-11 million.
Forgot that VGC doesn't track digital sales there. So I'll say 11-14m.
Bonus question: I think the first game had more memorable moments, while the second offered a rather unique experience that I also appreciate, and will use as a bar to compare other similar stories to in the future.
I prefer the first game though.