In Heinlein's 1966 classic "The Moon is a Harsh Mistress" the loss of self awareness in Mike (HOLMES) the computer struck me indelibly in my formative years. This speaks to Robert A Heinlein's tremendous abilities to develop his characters.
I can't think of a better example of a human created computer become conscious that was 'likable'. Hal was most definitely not likable in "2001: A Space Odyssey" and that film was from the same era.
What was the earliest appearance in SF of a likeable AI character? I'd like to read that book.