So, there is the State Department's classification of languages by how easy they are to learn for English speakers, which shows a wide variation. https://en.wi

So, there is the State Department's classification of languages by how easy they are to learn for English speakers, which shows a wide variation. https://en.wikibooks.org/wiki/Wikibooks:Language_Learning_Difficulty_for_English_Speakers https://en.wikibooks.org/wiki/Wikibooks:Language_Learning_Di... Of course, this classification is explicitly meant for native English speakers and includes the degree of relatedness to English as a contributing factor. I don't know if someone has done research about the average difficulty of each language as L2 considered across everyone in the world, but clearly there will be some that are easier and harder on average, considering factors such as unusual phonemes, non-alphabetic writing systems, irregular orthography, irregular inflections, presence or absence of inflections, similarity of sentence structure to most common sentence structures, and so on. Chinese probably has advantages as L2 due to the lack of inflections but disadvantages due to the extremely difficult writing system and (maybe?) tones -- just because I think most languages worldwide are not tonal. English has advantages due to the alphabetic writing system and disadvantages due to irregular verbs, irregular orthography, and some relatively unusual phonemes. Also, a lot of non-Chinese speakers already speak languages that are related to Chinese and/or share part of their writing system with Chinese, while a lot of non-English speakers already speak languages that are related to English and/or share part of their writing system with English. Anyway, we need to look into this a lot more before just saying that one language is a clear winner, but the idea is not at all meaningless and should in principle have an answer. Although clearly there will be some people who will be at a huge advantage or a huge disadvantage in learning any given L2, which is, again, a big part of what the State Department ranking is showing (not just the inherent ease or difficulty of learning each of these languages in the abstract).