There's no real practical reason to ask "who wants to be a millionaire?" because the only people who won't put their hand up are religious types who've taken vows of poverty and those who are already multi-millionaires. Unfortunately, there's a big gulf between those who want it and those who do the things to make it happen.
Based on recent statistics on UK household income, millionaire-dom is not something that's going to happen for most people, even with the dubious benefits of inflation. An adult earning the median level of income (£26,200 a year in 2011) and saving an impressive 20% of that would need almost 200 years to save £1 million (excluding taxes and investment gains). It's pretty clear, then, that a would-be millionaire has to think outside the boundaries of "median" experience.
Start a business
There are certainly people who can become millionaires by working for other people, but this is not an especially good route to choose. The trouble with trying to become a millionaire by working for other people is that there are always other people siphoning off the value of whatever you produce. Say you're a hotshot salesman – although you're going to get your cut, a lot of the value you create is going to get split among a broader pool of workers, managers and the owner(s) of the business.