that's why 4:3" monitors are still popular, right?
Video: no contest 16:9 is much better.
Books: The most popular book size in my library is 150x215 mom which is about 2:3 ratio but the text is printed in a 105x175mm area which is 9:15 ratio (much closer to 16:9 than 3:2)
Games: game developers are used to use 16:9 format for PC and console games, ports to other platforms are much simpler is this ratio maintained.
Web: most web pages are much longer than they are wide and fit much better on a portrait held 16:9 screen.
PD: I've both an iPad as an android tablet.