how long will it take to visit EVERY country in the world?

While clearing out my old filing cabinet, I piled all of my old passports into a box. Then I started going through them one by one. It appears that I have only visited 41 countries in my entire life. That may sound like a lot, but considering that there are around 200 countries, I'm only been to 20 percent of them. Out of those 41, 20 are EU countries.

When I was a kid, my biggest dream was to see every country. It appears that if I dont' get off my butt right now, my dream will never be realized.

Since it will cost a ton of mony to actually visit every country, I think my goal is to collect passport stamps from every country. For example, on a mileage run a couple of years ago, I flew SFO-ICN-NRT-HKG-SIN. In ICN, NRT and HKG, I only had enough time to go through immigration and come back to make my connecting flights. However, I did mange to "technically" visit Korea, Japan, and Hong Kong.

I figured there must be members of this forum who have already done this. I would love to hear from them on the best way to accomplish this.

Thanks in advance!