I have some ponies from all gens, so instead of choosing "One Gen to Rule Them All" I'll give my favorite for each generation instead.
Gen 1: SS Bouncy! She was my first pony, and I got her for my fifth birthday, so she has a very special place in my heart! I still have my original Bouncy, but her flocking is in pretty bad shape, so I have another Bouncy with gorgeous flocking and one that was baity that I deflocked. And Baby Bouncy. And a G4 custom Bouncy. You know, I guess I have kind of a Bouncy army!
Um if your Bouncy would like to be de-flocked feel free to sell her to me for a loving home =) I have a massive list of de-flocks to capture, obtain, posess, mwahahaha... oops I mean invite =)
My favorite today is sunshine. I am musing on sunshine and I love her big chunky metallic symbol and dainty blue. Actually that was this morning. Now I'm musing on Skyflier