Later, on hearing the recipient had much enjoyed the book, I said, "Oh yeah, that's always been one of my favorites."
It occured to me afterwards that it's perhaps odd for a grown man to have favorite picture books, and while it's true that I didn't necessarily take time out to read them before I had kids, I easily could have listed off a dozen or more favorite picture books at any given time. Perhaps we have bookish enough readers that this will not seem terribly odd to you for an adult to have favorite picture books. Either way, the following is a rather slap dash listing of favorites with a few notes on why -- making use of Amazon links since it's the fastest way to get images in on all these.
There are several other Frances books, all of them charming, but A Bargain for Frances is a favorite because of its lessons in negotiating and diplomacy for the 3-5 year old.
Ignore the later sequels, but the original Babar books are imaginative and charming in the extreme. From The Travels of Babar comes the useful line, "I've had enough. I'm going to smash everything." And I find that I still read the books in the same tone and cadence I recall from the voice of the reader on the Caedman audio books we had of Babar when I was a child. (Does this mean that our children will someday read the Narnia books with the voices of Kenneth Branaugh and the other British actors recruited to read the audio books they listen to all the time?)
What child does not at times wear his wolf suit and make mischief of one kind and another?
Although I'm fond enough of Peter Rabbit, I like Squirrel Nutkin, Jemima Puddle-Duck, Tom Kitten and the Fierce Bad Rabbit at least at much. Plus I can't help noticing the salutory moral involved in all of these stories being about foolish or mischievious animals being nearly killed and/or eaten.
As with Babar, I dislike all the later knock-offs, but the classic George books are quite enjoyable and the source of several household favorite lines.
Sadly, one of my favorite series of picture books in pretty thoroughly out of print, and very expensive. Graham Oakley's Church Mice books were very British and utterly charming. Now, however, they seem to be selling for quite a bit used.
I'm sure I've missed some favorites, but these seem to hit the high points.