Even if I could freeze the world for 10 years I still couldn't make a game that looks and plays like these, with the tools and skills and resources I have...
Simply: Don't. Don't try, don't want to create such games.
Assassin's Creed titles are sh*tty games in my opinion, they are so boring and incredibly repetitive. The same goes for many other AAA titles, they are simply no fun to me anymore, approx. since CoD: MW1 (which was a pretty good game though) most blockbuster games just try to streamline a cinematic experience. This hurts the gameplay a lot, and I basically find this to be not debatable. For example I really like the shooting and general gameplay of Max Payne 3, but I hated the game and could not complete it because you were interrupted every 10 to 100 seconds at max, cutscenes all the time or the game simply took control of your character.
I don't want to say that indie games are the holy grail (because they are not), I dislike most of them too, but oftentimes they take a better approach in terms of fun gameplay and they can do that because they don't have to appeal to a mass audience.
What I can suggest is that you try to create or think of fun mechanics first (Assassin's Creeds mechanics are mostly not fun, when you are climbing around you simply hold a direction or press a single button, no challenge, no fun, same for Uncharted, Tomb Raider and the like). Then or even before that think of your setting, your world where the game should take place in, and with of of that in mind think of a perspective for your game (top-down GTA 2 style, angled bird's eye view like in handheld Zelda games, side-scrolling in 2D or 2.5D, ...). A 3rd person or first person perspective is not recommended, except when you go for a highly stylized design (checkout AaAaAA, the A7 game Gravity or its semi-sequel/ remake in Unity "for the Awesome").
My personal discovery during the last year: You can create nice visuals by simply using plain colored textures (or greyscale and tint it dynamically) and then use those as a base texture for some material and shader effects. This saves a lot of time and work.
Or take the similar graphical approach of Super Mario Galaxy 1 or 2 (google images), just don't ever use normal mapping (looks horrible in 99% of indie games) and don't use the default lighting material.
