Persepolis In Pictures

I found this review for the film, Persepolis and what really caught my attention was the section that says:

If “Persepolis” had been a conventional memoir rather than a graphic novel, Ms. Satrapi’s account of her youth in pre- and post-revolutionary Iran would not have been quite as moving or as marvelous. Similarly, if the movie version had been conventionally cast and acted, it would inevitably have seemed less magical as well as less real.

I can't help but wonder why the conventional memoir wouldn't be as moving as a graphic novel and why a conventional movie, rather than an animated one, would have seemed "less real". I've always equated images and animation with fantasy, rather than realism. But I also find myself agreeing with the point that Scott puts forth. 

I'm not even sure why that is but I wonder if anyone has a response? Is it because of the nature of the narrative? Or is it because Persepolis has already been written in the form of a graphic novel that conceiving it in any other way seems difficult?