German is spoken more
French
French is more commonly studied and spoken worldwide compared to German. French is an official language in more countries (29) than German (6), and it is also one of the working languages of the United Nations, making it a more widely spoken language.
French is a more popular spoken language in Europe than German
Spanish is more widely-spoken than French.
Spanish is currently more widely spoken as a first or second language, but French has close to as many speakers with good proficiency as Spanish.
French is the third most widely spoken language in the world, behind English and Spanish. This is because England, France and Spain colonized large areas of the world during the great days of exploration. Everywhere they established their colonies, their language became the language of local society, culture, and international commerce. Long after the colonized areas became independent nations, the language continues to be used to this day. Germany was never a major colonizing power, so their language was not introduced all over the world in the same way that the other 3 languages were.
If you can only choose one, you'll probably find French more useful. French is much more widely spoken in the world than is German--unless you're very interested in Eastern and Central Europe and planning on working there, German really isn't spoken anywhere else in the world. French is a much more common first or second language, and is spoken in most of Africa, parts of North and South America, and some of Southeast Asia and the Middle East, besides being spoken in Europe.
Definitely French :) everyone wants to learn it, and it's especially more popular in schools. German is popular in Eastern Europe and across the European continent to a lesser degree. However, French is desirable all across the world on account of French being the language of diplomacy and the vast former French Empire.
The main languages spoken in Brussels are French and Dutch. French is more widely used in the city, particularly in government and business settings, while Dutch is mainly spoken in the northern parts of the city. English and German are also spoken by some residents due to Brussels' international character.
Spanish is spoken by more people around the world than French. Spanish is the second most spoken language in the world in terms of native speakers, while French is seventh. Additionally, Spanish is widely spoken in Latin America, which has a larger population than French-speaking regions.
"better" isn't really fitting. German is easier to learn, but OTOH Germans seems to be a bit more eager to learn English than the French is. This would make French the "better" choice for improving your ability to communicate with Europeans.
The choice between learning French or German depends on your specific goals. French is spoken widely across the world and is an official language of many international organizations. German is important for opportunities in industries like engineering and technology, especially in Europe. Consider your career aspirations and personal interests to determine which language is more important for you to learn.