This is the best of the five games I've claimed as the hardest ever. This is actually one of the better PC games of all time, in my ever so humble opinion. But you can boot it up right now and I guarantee that you won't beat it within the next 2 weeks.
The game starts off slow and chill. You have your quaint lil' hospital wing where you only have to make your office and a diagnosis room and then maybe a pharmacy. As the game progresses though you start getting more and more people with strange diseases that you think you know how to treat but in actuality you do not. You fail. Here is a not uncommon scenario in Theme Hospital. I've written that from the perspective of an imaginary patient named... Dennis, totally random. As I sat in the doctor's office I noticed he moved like a scripted sprite. My head had swollen up to balloon like proportions. I had been diagnosed with 'Bloaty Head.' I'm pretty sure that's not a condition recognized by...anyone. I was told to go into the 'Deflater Room.' This worried me. My anxiety was heightened when I entered a room with what looked like a huge bicycle pump with a monstrous needle on the end. For 3 hours I sat in that room until finally a doctor who moved like a robot entered and stuck the needle in my head. My head popped like a balloon and then the doctor inflated my head just a little (I was hoping he would make a comment like "Oh you always were full of hot air!" but he just left). This shattered my universe since I had just learned the human head is comprised of ...air. As I was opening the door to leave there were roughly 300 people roaming the halls. Some had the big head thing like me but most were just throwing up. Amazingly there were about 6 janitors in the hall cleaning up the mess. I even watched as Janitors suddenly appeared out of the air and started cleaning the messes...
It will get to a point where people will just throw up which causes other people to throw up which causes a chain reaction that will make you hire like 10 janitors in one minute to try and control the situation. 2 janitors could do the job but they tend to clean one mess AND THEN GO INTO THE BREAK ROOM. Yeah I hired you to mop up one pile then go chillax with the MD's. No.
About 10 levels into the game it just gets maddening and you are overwhelmed with patients with ridiculous diseases that you really just don't want to cure because they piss you off. Oh and did I mention that you also have to budget research money so you can even treat theses people? Because that really is awesome when you have a hospital of people heaving all over. Researching. Hard game.