I didn't play prototype, but from what I've seen I'd say "no". Divinity has a story, it has a backdrop, it has lore. It has quests and interaction with people in the world. Your choices are not always black and white and there are some interesting outcomes. You can not necessarily "complete" all quests for example, as your choices may preclude some quests from finishing.
I guess I don't like to shoehorn games into any particular type. It is what it is, and I'm sure it isn't Prototype =)
