Shoulda had a poll...
EDIT: Shoulda looked up...
iPhoto is more of a library then an editor (although it has some very rudimentary editing functions), if you need some serious editing, then you can set iPhoto to use an external editor, e.g. Photoshop.iPhoto is fairly useless to me, as I'm accustomed to using photoshop for serious editing.
Should iTunes count as an iLife app, seeing that just about everybody, PC or Mac, has it?
If it doesn't count, GarageBand is my favourite. You get so much product for such little money! People who have bought recording software other than GarageBand know just how much of a godsend it is