Champions League has the best football on show. Quite simply, players are more comfortable and more used to playing alongside their clubmates rather than their countrymen because they just spend more time with their clubmates. There's more fluidity in the quality of football, and the tactics are far more complex. Moreover, there's always much more at stake. Some clubs may have already been knocked out of their domestic title race and are just hoping to win the CL as salvation. Sometimes the manager's job is at stake depending on the CL performance. The ties are also played over two legs, so a team can't just rely on a 'fluke' victory - they have to win over both ties.
The WC is the stuff of legends though. Puskas, Pele, Maradona, Garrincha, Ronaldo, Zidane, Cruyff, Beckenbauer... these names have graced the stage of the World Cup. Not all of these have also graced the CL though or experienced any success there (e.g. Ronaldo, Pele, and Maradona). Since the WC is also more infrequent, it is also more memorable. The WC has a way of bringing together the people of a country - regardless of whether they watch football or not. Even if your country isn't playing in the WC (Canada), your people always watch it because it's such a massive event.
I do, however, disagree with the opinion that the WC is more important than the CL. It is more memorable because it is so infrequent and because it is easier to identify with a nation rather than a club. But true talent is shown on the CL stage where the opponents are more difficult and where the quality of a team isn't dependent on how fortunate you were that you were born in Germany or Brazil, etc. Messi winning the CL 4 times tops Pele's 3 WCs for me.
tl;dr CL > WC. Euros don't even come close.
P.S.
If you're wondering why I think this way it's because Pele was bloody fortunate that his countrymen during his era were also some of the greatest players of their generation (and in some cases, greatest of all time). Messi's Barcelona has also been stacked with talent, but it was talent that was assembled. Somebody decided to sit down and think about which direction the club should go in the near future, and that meticulous planning led to the likes of Messi, Iniesta, and Xavi. Moreover, Messi had to hurdle bigger challenges than Sweden in the final. All you have to do to win the WC in today's game is just win 7 games in a row (or even 6/7 victories is enough to win the competition). If you're looking to win the CL, there's a lot more you have to do in order to win.
Brazil's, and Pele's, 3 WCs were thanks to sheer luck that their squad happened to have some of the best players in their era, but Messi's 4 CLs are a result of long-term planning and hard work.
Which do you think is better as a competition? In your opinion, which tournament brings all of what footy really is about. The action on the pitch, the atmosphere, the quality on display.
At work we have been having this debate for about a week now. We all watch and play (or have played) before so we know the game well. We all follow the leagues and the players so the debate is rather interesting. For me, the top two competitions are the World Cup and the Champions League. The Euros are a very close 3rd.
The World Cup needs no introduction. It is on a global scale that no other major tournament can match. It bring in fans from all over the world and "usually" has the best national teams show what they can do at the highest international level. As a fan of the sport and for the entertainment value, the World Cup is un-matched. The quality on the pitch is very good for a number of teams and it carries a count of stories that will hold the world captive for it's run of the month.
What the World Cup lacks that the Champions League has is overall quality. To be fair, there is a big difference in a major Club team level and a major National Team level for a few reasons. The main reason is how much time they get to play together. National sides supposedly carry the best their nation has to offer so individually, you would consider the team to be better on paper. Given time, they would be better of course, but they don't get that time. Club teams practice day in and day out, then play so many games together that it takes the player relationships to another level.
For quality and being a pure fan of the game, the Champions League is the best in the world. For the show of the game and the entertainment on a mass scale, the World Cup is best.
I could go deeper but I ask what your thoughts are on this.