Oliver - I prefer the sound of it to the other names, even though it is really popular where I am (number one).
Jack would be my second choice but only if it was a name in it's own right. I don't care for it as a nickname for
John. A few years ago I was sick of the name
Jack as it was number one forever here, but now I can appreciate it and can also understand why it became popular.
Henry - I know a lot of little Henrys (it seems to be the default name for middle class parents to choose) so I'm getting a bit bored of it. Also I find it to be a bit pompous sounding.