Which is the best soccer team of all time?
It is hard to say since there could be multiple rankings to answer this question. 

Assuming the best soccer players end up playing in Europe, we could take into consideration the European Champions League winners. Using this ranking, Real Madrid, having won 14 trophies, could be considered the best soccer team in the world.

Alternatively, Fifa awarded Real Madrid the “soccer club of the 20th century” after winning a popular poll with 42.35% of the votes.

Everything around soccer teams is very subjective and feelings could play a big part for everyone's answer.