I love the Queen Leech. There, I said it.
And it's not some guilty pleasure of mine. Not the "so bad, it's good" type of deal. I genuinely find this villain engaging and perfectly fitting for what the BIO series represents. It may have outdated animations and not the best voice acting, but its overall concept is pretty clever.
Essentially, the Queen Leech's image is based on Christian imagery. It's almost surreal to me how many fans talk about Sephiroth and other Final Fantasy bullshit, but almost no one pointed out that long hair, a white chiton and a cross necklace are attributes associated with Jesus Christ. And one of the ideas for the title screen substantiates this association by representing a leech in a composition reminiscent of the Cross of Golgotha:
Such mimicry, of course, is an extension of the mind of James Marcus himself, who, according to the guidebooks, considered himself a god and dreamed of regaining his beautiful youth. Although don't let the leech deceive you, because in fact it is not a resurrected Marcus, but merely an imitation of his thoughts. And that's where the mythological connotation arises: James Marcus, being the figure of the Creator, breeds a new species of leeches (basically mold them by the Clay Virus) and bestows these animals with fatherly love, to which they reciprocate. The last evolved leech, merging with the corpse of its Creator, becomes the "incarnation" of Marcus in a way similar to how Jesus was the incarnation of God in a human body.
Once dreaming of creating neo-humans, Marcus' very essence is now embittered at Umbrella and humanity through the body of a leech and intends to send sinners to the depths of Hell, thus beginning his own Last Judgment. And this act of godhood ultimately leads to a catastrophe in Raccoon City, which an official source compared to Sodom and Gomorrah. It's a pretty consistent narrative that adds a layer of complexity to the series' plot.
When fans write that the interpretation from The Umbrella Chronicles is better because it looks more realistic, I am given to disbelief. To think, interesting ideas and nuances can be easily exchanged for pseudo-science to remain pseudo-science. Part of my enjoyment with the BIO series stems from the fact that these games are aware that they are, inter alia, Gothic fiction, so they tell engaging stories within that paradigm. When you think a lot about which idea is more like the real world and which is not, you may forget what your series stands for. This happened to the developers of RE:2 when they almost cut out an alligator.