Though, alright, let me put on my best suit, slick back my hair, and give it my best
Keanu Reeves impersonation:
Gwen Stacy and Mary Jane Watson come from two different eras of storytelling. Gwen is a hero's girlfriend in the very Silver Age style; she's no worse an offender of the "bland, personality-less beauty designed to be put in mortal peril" trope than, say, (classic) Iris West. Hell, until ol' Spidey and Marvel came along, even the
heroes hardly had character traits beyond "always does the right thing" and "reminds kids to eat their vegetables." So to completely compare the two without considering their relative context is a bit misleading.
Still, as Gerry Conway is quick to point out, no one cared about Gwen Stacy until
after he killed her. That's when the cult of personality around the character really began.