Pls let me know if this was not the right forum for this subject
I don't know about IPad, but my baby seems to like "Toddler Teasers" on my IPhone.
i LOVE the PBS apps, superwhy, curious george, etc for my 3 year old dd
theres also an elmo one for tracingv letters that she love!
My 3 year old likes the Toca Boca apps, Peek-a-boo barn and peek-a-boo wild, Bugs and Buttons, Dr. Suess Band, Doodle buddy is a free drawing one, there are almost all the classic Dr. Suess books on there, they are pretty good, it will read the story to you or not if you want to read it outloud yourself.
I second Toca Boca apps and Bugs and Buttons. We use our ipad heavily so no judgement here
Montessori 100 board, Toca Boca, ZooWho, Read Me Stories, Miss Spider (stories), TinkerBell, and Phone4Kids.
ETA: Phone4Kids has no educational component whatsoever, but DD loves it.