It is a running gag on the comedy site Cracked (and perhaps elsewhere) that holodecks would be mostly used for sexual fantasies, but I would like to ask hypothetically what the most common fantasies would be (other than sex). Maybe being a celebrity in front of an adoring audience, or getting revenge on one’s enemies, or creating some computer-generated friend or mate?
I suspect the most popular holodeck fantasies would be variants on being wealthy and/or adored by everyone.
I suspect that Jean-Luc Picard’s choices (playing a character in old fiction that he enjoyed) would be a popular sort of choice. If I had access to a holodeck, I’d love to play in programs based on Star Wars or The Lord of the Rings.
For men they would be sports star, super hero, cowboy, space explorer. For women it would be princess, singer, celebrity.
Role playing - spy, soldier, hero. Luke Skywalker, James Bond. Dixon Hill. Captain Proton. 
Second, doing things you can’t do or are too scared to do. Skiing down Everest, climb Half Dome’s face, freefall from 100K feet, surf a 100 foot wave.
A big thing would be recreating happier times in your life.
Reliving when you were a kid surrounded by family. A really happy vacation or holiday memory. Reliving being back in college or high school. Times when you felt happy and safe.
And I see a lot of very realistic, first person shooter video games.
I never paid attention to the ins and outs of Star Trek lore – Are holodeck experiences “private”? I’m picturing someone running simulations on assassinating the [figure] and getting a visit from Star Fleet Secret Service.
Shooter games and other violent fantasies would be big–ninjas, jedis, and the like.
Exploring glorious locations–a la the spectacular computer game Subnautica–would probably be popular.
Finally, if a holodeck could come up with a way to make you feel like you’re flying, that’d be huge.
Sort of private but probably not enough privacy to work on your evil plans. Basically, if any of the senior officers want to find out what programs you’re running, they can check or they can just walk in while you’re running them. If you don’t give them a reason to look, then you’re probably OK. Covering up anything after the fact isn’t going to work though.
I would imagine you can’t assume they are private, and that only people rich enough to afford holodecks (not connected to anything external) in their private residence would really feel safe that nobody’s spying on them, just like someone playing games on his/her own PC in their own living room in real life.
Homesick crew would recreate their hometown neighborhood and families.
I think the holodeck could be combined with the equivalent of our modern day FaceTime.
So you could go to your parents house and actually talk with them in a familiar setting.
The Face Time feed would interface with the holodeck program. It could even create those characters for you.
This - and related, I think historical voyeurism / participation would be big, especially with advanced technology improving our knowledge over time.
You could live in Rome under Augustus, as an ordinary Roman, a patrician, and Augustus himself.
You could live through Newton’s greatest experiments / discoveries, as him or others, or be there for Lincoln’s or MLK’s or Nelson Mandela’s greatest speeches - and that’s just OUR history, they’d have a few thousand(?) more years to sample from.
My first thought was going back in history to witness a particular event or to observe life in another place and time. Based on what I’ve read in this thread so far, I’m pretty boring.
Not boring! But, perhaps, unrealistic? Unless they used time travel, I wouldn’t trust that the recreation was accurate. There are a lot of missing historical records because of the wars. Wthness Kirk’s knowledge of the OK Corral. The recreation made from his mind had half the facts wrong. You might role play in Henry VIII’s court, and find out they made Henry look like this.
Saw this at a GIS conference once. Can’t remember the company, but I will try to follow up.
You would strap yourself face down on a ‘bed’ that tilts on 3 axis. Your arms strapped to ‘wings’ that you would flap and turn. The simulation was oblique aerial photography that covered views from all directions that you saw in goggles. It was seamless, so you could ‘fly’ around stuff.
I would think that sports and hazardous hobby training would be a big draw.
One could practice the hazardous aspects of any endeavor without risk of injury.
You could configure the simulation for rock climbing Ski jumps, fast vehicles, alligator wrestling, whatever.
I don’t believe this was ever addressed in cannon but obviously the starships have some manner of artificial gravity. Can the gravity be manipulated specifically within the holodeck chamber? Can you create a micro-G environment? This opens up lots of interesting options.
I think the episode that Barclay was introduced in had it right. Your boss is a weenie who you can dominate and the sexy gal/guy you have a crush on loves you.
Possibly I’m the only person with this idea. But my biggest fantasy would be to basically re-create some of the Star Trek episodes, and actually be able to interact with Kirk, Picard, etc.