While I am willing to admit that sims don't always have reactions to what is going on in the game emotionally, there is also the other side of that coin, when they overreact or act out of character.
For example, in my recent sims 2 play, my happily married with 2 adopted children gay sim answered the door to an ex BF, he immediately began to passionately make out with him. A man he had not seen and had barely spoken to for literally years in game with his children and husband and the nanny standing right there! Husband was PO'd and relationship of years was tanked. This was so off putting for me as I felt it was out of character as well as unrealistic.
So, honestly, I prefer that sims don't have too much reaction, as opposed to way too much.