Winning the world cup takes a lot of work. Many countries can not devote the resources to grooming players from the under 15 though under21 ranks consistently. Further, access to club opportunities and other sports will also effect a countries chances (look at the US where soccer is probably the 3rd or 4th choice for most potential athletes).
Now this doesn't gaurantee success (see Portugal who had a few years where they absolutely ruled the U20 or U18 and had a group that included Figo that were supposed to be world beaters), and also not having the cash doesn't limit the chances (Cameroon and Nigeria have had flashes of brilliance, yet the lack of funds and clubs doesn't allow sustained consistent performances, while the likes of Brazil has many 'street players' bloom into superstars due to a rich club structure).
Now that is why European countries (especially ones with an established style and history in the sport) tend to do well. Argentina and Brazil also do well in this venue, mainly due to adopting the sport from European immigrants. That Europse is so soccer crazy, has 17 teams admitted (at the expense of some other possibly stronger sides) and that to keep sides from facing others of the same region they do the draw so that nearly every group has just 2 Euro sides (meaning a North American side might not play an Asian or African team depending on how they stagger the draw), puts the top power teams in situations where they will face weaker opposition.
The Associations in the bigger nations put a lot into the feeder systems, and to sustain that kind of momentum isn't easy or cheap. Look at how the former communist nations have fared since about the mid 80's. Sure Germany had a strong team (and even moreso with unification), but the rest tended to be one shot wonders. If you look at the talent on Bosnia, Serbia and other nations from the Balkans, you almost have to wonder how a 'Yugoslavian' side would look had civil war not caused the hardships there.
Italy, England, and Germany have had long runs of stability, and France farmed out their players into the best leagues around them (the three afore mentioned, plus Spain) and thus those 5 have had traditionally strong teams. Some teams go in power cycles (see France's domination 96-2000 with euro and World Cup), but now face an aging side with will prospect of replacements (Spain and Portugal are staring this train in the face).
And, lets face it, as good as Spain and Portugal are, thay have seemed to have fallen to bad luck time and again.
it comes down to a simple premise in sports: in most any league, you will find 1 or 2 dominant teams who win quite often, and then there's a small percentage 'won by the rest'.
Premiere league. Man Utd with 11, Arsenal with 2, and other teams with 2 or 3 if I recall.
USA's Major League Baseball. The NY Yankees have won the World Series at least 15 or 16 times.
USA National Hockey League: Montreal Canadians at one time owned the Stanley Cup.
La Liga: Real and Barca have owned it in the modern age, with other sides getting the occasional sniff.
Dutch Eridevese (First division): PSV. Ajax. Feyenoord. This year someone else took 2nd for the first time in a LONG time. Let alone a shot at first.
Being held every 4 years allows the reasource intense nations to zero in, get the right coach and side, and plod in with great expectations. Those able to handle the pressure rise to the top, and usually its the same mix of teams that fall in there. Will the tables turn over the next 20 years? Probably. Would I expect some surprises? definitely.
At the same time, I wouldn't bet much on an African or Asian tourney winner in the next 12-16 years (though the next one is in Africa, and home field is a HUGE advantage).
Some countries have bigger player pools, and when you can get a few thousand excellent players identified, and then have them playing each other (improving ability better than playing in mush leagues), the pool advances as a whole, and individuals might get even better. sure you will have the phenom's that pop up from small places like a Freddy Adu or Michael Essien, but, a nation like England will churn out very high caliber prospects (who are quickly snapped up by the big clubs who have them practice regularly with world class players further accellerating their development).
That they expect the success and its the norm also helps. england already has its eyes on Theo Wolcott of Arsenal, tagged as the 'next Rooney'. In such an environment, the expectation can be handled better than in some other places where a player trying to carry the hopes of a nation might wither (see landon Donovan's German adventure).
Some countries just have players that are that much better and more adaptable to the situation, and better facilities and coaches.
And thats why that exclusive club will continue to hog the awards at the major tournaments....
But, there is always the Olympics for the rest....