There are a lot of them I can think of these days. They are mostly inventions by men. They came out, were hyped and people got crazy. Some of them aren't things though. They are concepts that people hold but in reality have little significance
1.] Being a doctor or an engineer. When I was growing up, it was all I heard. Being an engineer or a doctor means you are made for life. You'll get employed almost immediately you leave school. Maybe it was true in the past but it doesn't work anymore. I've seen a number of first class engineering graduates roaming the streets and hustling for what they can feed on. Nothing is guaranteed anymore, not even being a doctor. Many of them offer their services for peanut, salaries that in no way justifies the effort they put into getting their license.
2.] Sex. This one still beats me. I've not engaged in the act but I've come to wonder why so many people attach so much importance to it. I've seen guys do the craziest things just to get laid. Is sex that important? Where is grew up, it wasn't uncommon to find guys doing hard jobs just so they could have enough money to get some lady to satisfy their cravings. It's not wise to me and I think it's badly overrated.
3.] Football stars. Many would not agree with me on this one but I'm actually not sure why people look unto footballers with such awe that some even consider them gods.
Football, quite alright, is a game of passion. It's a game that brings many people together but when you consider the extreme that people tend to go sometimes, you begin to wonder whether all of these are necessary. I remember the news of a young dude that killed himself because Ronaldo didn't win the Balon D'Or. I think that's foolishness. I love football but wouldn't go to the extent of skipping meals.
This is an opinion based question, so I will provide you with my opinion.
I think the most overrated "thing(s)" in this world are ego and pride.
It's also something I struggle with at times, but I recognize it as a weakness that needs improvement.
I can be a real asshole sometimes because of ego and pride. I've become better at noticing when ego or pride is a factor, and minimizing the effect in my reaction. First comes the thought, then comes the physical response. When you work on influencing your physical reactions, by taking notice to how the thought provokes it's response, you can become better equip to make appropriate changes to thinking patterns that are unhealthy.
Ego and pride, can be create very negative patterns, that others will recognize, and likely disassociate from. To me, this is the most overrated, or negative human character trait.
I'm not sure if this answers your question adequately, but I did my best.
The next on my list would probably be materialism.
Being wanted by women and getting laid.
Men get an ego boost from being wanted sexually by women and getting laid. Why would anyone want their sense of self-worth depend on the whims of other people? Particularly people as fickle as women when it comes to their desires? Do you seriously believe the females of our species to be proper judges of virtue and what makes a man great? Do you really think they should be granted this privilege? Who is of the opinion that women should be the gatekeepers of male sense of self worth?
When you demystify sex, you're left with a bunch of pleasurable physical sensations. Besides, acceptance and love by women are always conditional and contingent upon men providing them with their wants and needs. Being with women always comes with a cost.
Own a car
The Apple brand products.
The courtship, especially adolescent.
The university degrees.
Sports as a show.
The heavy metal.
The little Prince.
I would say ~ Commercial Space Flight!
Reading about it makes me "nauseous" :(
A price of $250,000 (by Virgin Galactic) is definitely one of the overrated things that a person would fancy. I don't even see the thrill of doing it if not for a reason to discover new existence or a new planet.
Surprisingly, even though it isn't in full operation yet, there are high-profile personalities that already signed-up for it.