Here is the recent idea that I've seen written about Data and emotion.
Dr Soon had already created an android with emotion, but Lore ended up being psychotic, so Data was created-without an emotion chip.
Data seems to go through all the motions of feeling, but cannot classify it. Like a gap is missing.
However, I like classical view on Data; He doesn't have emotions, he just has a set of desires and goals, and even those are programs.
Yet he stills tries to be 'human' but is always an sentient computer looking from the outside. He comes off more interesting that way.
It's true, after the movies gave him his emotion chip, Data became too gimmicky.
They went right back to giving him the ability to flip off the chip, even though it was claimed in the first movie, the effects was not reversible.