This is a classic story of a spoiled rich brat that gets a big slap of reality. Fortunately, this one involves a lot of weapons, a lot of action, and a lot of humor.
A move like this can only really be done justice by an actor that is truly suited for the part of the hero. Robert Downey Jr. is just that actor, and he pulls this one off in spades! No other actor could have done this justice.
As the movie progresses, the rich brat realizes the error is his ways, and he starts to fix his mistakes. Just a note here, when you are a brat, you make little mistakes, when you are an extremely rich brat, your mistakes are much, much bigger. Needless to say, he has a lot of mistakes to fix.
When you go to see this movie, don't be in a hurry to leave during the credits. There is a little surprise at the end of the credits.
Enjoy the movie, and save the bathroom breaks until after the credits have finished.