It is not strictly necessary, but it is recommended
The Silmarillion gives you an overview of the First Age. The Great Tales are stories that happen in the First Age, and they correspond to chapters in The Silmarillion.
The stories are not entirely self-contained, and a lot of reference is made to other events of Beleriand, which you'll be familiar with if you have read The Silmarillion first. That said, Christopher Tolkien attempts to compensate for this with a long preface and an glossary/index in the back.
It should also be noted that of the three Great Tales books, only The Children of Húrin is even a proper narrative story. The other two books are out-of-universe studies about their stories' respective external histories, showcasing a few different versions of the text to see how it evolved over time (similar to The History of Middle-earth). And as such I'd say that those other two books are significantly more difficult to read than The Silmarillion.
The essay "A Rings-Reader's Bridge to the Children of Húrin" by Steuard Jenson may be of interest to you; it is designed for people who want to jump straight from The Lord of the Rings to The Children of Húrin.
And as a final note, this answer also applies to the two First Age stories inside Unfinished Tales, which are both just examples of Tolkien's Great Tales writings, and which reappear in those books.