Understand when I say this that I'm enjoying Destiny. I play PvE all the time. However, I've played COD for years and typically max prestige there with tons of the golden guns. So I can tell you the difference. The first difference is the reward system. In COD yes you have to grind to get what you want but there are specific well defined steps to each task. In Destiny most of the rewards are based on random luck. That doesn't sit well with some folks. Personally, I play so much that even with random luck, I'm going to get my reward. Not everybody plays as much as I do though and those folks feel like they are wasting what little time that they have to play when they put in the hard work and have zero reward to show for it. In other words, there is no light at the end of the tunnel for them. Now to the next difference and that is the PvP. I know you didn't want to compare modes but most die hard COD players play it for the multiplayer. That's just how it is. If you like CODs MP then it's really hard to like Destinys PvP. They are two completely different animals despite having similar gamemodes. COD players hate instant kill devices and Destinys PvP is full of them. Personally, I loathe playing Destiny's PvP. I can do well in it but its just not as competitive as COD MP. Destiny PvP is just not fulfilling in my opinion. Thankfully though Destinys PvE is straight up awesome. CODs campaign is cool but it lacks replayability. So in the end you have two games with loosely similar features but each one does some things much better than the other. If you are a person that can only appreciate one of those features then you will have a favorite title. If you can appreciate both then you might have two favorites.