A great game that has had me hooked since childhood!
Theme Hospital is a game that has never gotten old for me, every now and then I still go back to play it despite its now outdated graphics and gameplay. I find the humour refreshing, the graphics aren't bad for a game that is now 14 YEARS OLD! And the level of fun is very high even after hours (in my case years) of play!
GS is right in saying the AI can be a bit stupid at times, but I think that is what is to keep you busy, luckily you can just pick a doctor up and drop them in a room and they will stay there as long as they are not tired and the handymen will clean the place if they are dropped nearby. I think without this intervention by the player there would not be a whole lot to do, you would just sit there and wait to either go bankrupt or watch the money flow.
Discovering all the humorous and strange new illnesses is great and watching how the patients are 'cured' is very amusing this game is not given enough credit for its simplicity and fun. I would recommend picking it up but chances are you will never find this one in a shop and good luck on eBay because I don't think I'll part with my copy ever!