First of all, they are all good games, you can't really make a bad choice. I would recommend playing all of them eventually.
Personally I think Wolfenstein is the best, followed by Metro, then Far Cry 4. Wolfenstein had that over the top, old school FPS feel that I find most enjoyable, but it also had a surprisingly good story. BJ Blazkowicz was far more than just the dumb grunt that I expected.
Far Cry 4 is good, but I didn't enjoy it as much as FC3, which I loved. I think my enjoyment was hindered by the feeling of "been there, done that". There is a joke about Ubisoft: The Game, but that's how I felt when I was playing FC4. There are so many mechanics shared between Far Cry, Assassins Creed, Watch Dogs, etc, they've all started to kind of feel like the same game, so each one that comes out feels less and less exciting.