Like everyone else I suppose it depends on the circumstances you meet and what is going on in their life at the time. They're just human beings. They have parents, siblings, and friends like everyone else.
It's the fans and media who turn them into consumer products.
Some of the comments you see written about celebrities at the bottom of online articles you'd believe most people don't think celebrities have feelings. They're shredded for gaining weight, losing too much weight, clothes they wear, performances in movies or whatever, comments made about their children and significant others/spouses. Paranoia can be mistaken for narcissism.
No matter how popular a celebrity is they have their "vocal haters"!
Everyone is entitled to have an opinion about current events but if a celebrity shares theirs they are often ridiculed by one side or the other. Essentially they're just "court jesters" who should remain quiet.
We as a society "dehumanize them" and then we're shocked when they're not friendly as we ask them for autographs while they share a meal with their family in a restaurant or use a bathroom stall next to us, relax on the beach, or take their kids to Disneyland.
No one can be "on" 24/7!
Some of them have had insane stalkers (break into their homes), send hate mail or threaten them. Sometimes the perception of them being narcissistic is nothing more than their desire to find moments of privacy. Generally that requires staying in exclusive places and associating with people who are in the same boat as them.
Most celebrities have sponsored charities and other causes, participated in "Make a wish foundation" and the like but no matter what they do or how much money they donate it will never be enough for some folks. Maybe people's envy and jealousy is at the root of it.