D&D 5e sure, but that's not really enough. For me the big draw is the Forgotten Realms campaign setting.
One of the issues I have with trying to pull something like this off outside the Realms is that I just don't care nearly as much when it's an 'original' IP, and I'm way too precious with the other official D&D settings.
FR is my preferred knock-off setting.
This is a big deal when devs look at designing an RPG. The Realms has a WEALTH of lore for players to deep dive into. Want to know more about Illithid and their ways, well there are a ton of books and articles available. Want to understand the worship of Shar, again a lot of material. The realms are one of the most fleshed out fantasy worlds a RPG dev can find. New IPs have the issue that they have no lore to fall back on. I have been having this discussion with the folks that made Solasta. They offered a lore book to a few people and then pulled it after Kickstarter. That book, or even a smaller version would be amazing for a lot of us as it would give us more lore context.
