another point
spanish is only the most widely spoken language by population which i think is not a really good indication at all. A much better list is to look at the number of countries where it is a first language, then the list looks more like this.
English (115)
French (35)
Arabic (24)
Spanish (20)
Russian (16)
German (9)
Mandarin (5)
Portuguese (5)
Hindi/Urdu (2)
Bengali (1)
Japanese (1)
and to take it further
After weighing six factors (number of primary speakers, number of secondary speakers, number and population of countries where used, number of major fields using the language internationally, economic power of countries using the languages, and socio-literary prestige), Weber compiled the following list of the world's ten most influential languages:
(number of points given in parentheses)
English (37)
French (23)
Spanish (20)
Russian (16)
Arabic (14)
Chinese (13)
German (12)
Japanese (10)
Portuguese (10)
Hindi/Urdu (9)