Yep, As someone said it's more likely that you will die from a lightening strike than becoming a Billionaire Becoming a Millionaire, however, within our reach...have to keep looking around (for ideas ) and keep working on them.
Let's see... How many pageviews/day you might need to become a millionaire in 5 years from adsense alone... Lets take ctr 1% , Per click average 0.2$ and 5 years is 1825 days. Number of page views required per day = (1,000,000/0.01x0.2x1825)= 273,000 273,000 page views per day required! very few amongst us can reach that number.Very Difficult...but impossible? i don't think so. And of course its just on averages...for example if some how you could raise CTR to 10% you may require only 27,300 pageviews per day.
Go outside and make a million friends and ask if they can give you $1 each. After that, you'll be a millionaire.