Well Judaism, Christianity, and Islam only have one God, not a pantheon of deities like the other religions. It wouldn't incorporate into the game well (imagine playing as the Abrahamic God, AKA all-powerful being. It wouldn't balance well). There's also no really interesting myths associated with any of the figures (who are all human, and not deities in themselves but merely a representative for God). Couple this with the fact that there would be a massive backlash if you could play as Jesus, and it makes perfect sense why they made this decision.
@OhSnapitz Well technically seperation is the point of conventions. It's a group of similar people who get together, in this case it is homosexual people who enjoy playing video games.
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