IMO the actual gunplay is better in COD/Titanfall/Battlefield. Is there really going to be that much exploring? I have yet to see how big the game world and levels will be in total for the retail release. Now having said that I think the story/upgrading and universe of the game will warrant a purchase for me but as far as the gameplay and lack of physics in the game I am not impressed at all considering how hyped this game is and the massive budget
The worlds we know about are The Moon, Earth, Mars, Venus, Europa(jupiter moon). Each world will have an area that is as large as the entire game world in Halo Reach. What we play in the beta is Old Russia: The Cosmodrome. That's a very small slice. A lot of areas in the cosmodrome are blocked currently as well.
Perhaps you're looking at it from the wrong perspective. It is not meant to be entirely single player, it is meant for you to explore, find items and chests, collect various resources and do various missions for the hub city with people. When you turn in these bounties and complete the missions you are rewarded and you turn those rewards in to get new armor and weapons. If you didn't explore, you missed the whole game already. There is a story, one which will have a huge amount of lore and a ton of mystery to uncover. That is only a part of the game, the meat of the experience is in exploration, public events that happen as you explore, and the strikes and raids that require a team to complete.
Also do realize that this entire game is played connected to an online server with the possibility of meeting people in the game world at any time. The games you mentioned are much smaller in scope with scripted events. What you call physics is actually pre-programmed and scripted in to do a certain thing. That doesn't work when you have a game world that is connected to everyone. I gave up on Titanfall after a week...I've played 20 hours in the Destiny beta and I never once felt bored or uninterested in it.