many people正确，people本就是复数名词，而且是可数名词。

many和much都意为“许多”，但 many 修饰或代替可数名词（复数），与 few（少数）相对；而 much 用来修饰或代替不可数名词（单数），与little（少量）相对。

如：

Did you see many people there?

你在那儿看见许多人了吗?

Many poets have died young.

许多诗人很年轻就死了。