At 2/3 dd was into
Boyton
Babar books
The Grey Lady and the Strawberry Snatcher (totally weird book)
at 3 and 4 suddenly she wanted all the 'information books' on space I could get my hands on...
now she has gone around the twist for HEROES. super heroes of any kind, so we are on easy readers and some comics.

At 2 ds(now 10) was very into
Thomas books (we had a large set and they were in constant rotation)
Gaga for Boyton (esp. pajama time & going to bed book)
Nursery Rhymes, especially the huge Rosemary Wells book in red...that thing got nightly use, I can still probably recite 75% of it in order by memory.
Almost any book was just a delight to him.

Later on (4/5-ish) he dug captain underpants, and I would read the Harry Potter books to him which he LOVED.