It depends on what your native language is. For example if your native language is English, and you have the options of learning Spanish or Chinese, then Spanish will be easier, one of the reasons being because Chinese is a language very different from English, there's no actual alphabet and there's lots of sounds in the Chinese language that the English language does not contain. It's the same problem with a native Chinese trying to learn English. There's many sounds in English that a Chinese person does not use. However, it could possibly be much easier for a Chinese person to learn Japanese or Korean because of the similarities between both the spoken language and written characters.