First off Destiny is more talk than fact so its hard to say how their proposed ideas will turn out. That being said assuming everything we have heard turns out more or less identical to the ideas they are proposing It would be a pretty perfect fusion between shooters and rpgs. It borrows enough from each genre to seem like it belongs there but has enough foreign elements to not really fit in comfortably with any other games in that genre. Simply put I think at this point there really isn't a good model to compare this to. TL;DR: Destiny will be in the Destiny genre.