Wing Commander - I'd do a complete reboot and have it integrated with live action videos (like what Quantum Break will have and what some of the later Wing Commander games did). It would have a grittier Battlestar Galactica 2004 feel to the ships.
Dark Souls 3 - Large open world with no random encounters with a post-apocalyptic anime vibe. I'd probably also have the main character encounter a sidekick who doesn't actually fight with him but may do some interesting things on its own. I'd flesh out the story a lot more and have at least one town with citizens in it.
Gears of War 4 - You would basically start the game alone but could find allies in much the same way that it's done in the Mass Effect games (with some that are trickier to get like Legion in Mass Effect 2). I'd add similar rpg elements into the game like Resident Evil 4 has. The game would take place centuries after Gears of War 3 with very large cities (with skyscrapers) and the locust/etc thought long extinct. There'd be another emergence day complete with new and old enemies and the game would take place in one of the largest cities.
Halo 5 - Master Chief would be seen as a relic of the past and his warnings not taken seriously. He would be seen outside of the suit for the first hour or two of the game. One part of the game would have the Chief fighting one or more of the Spartans and another would have him rallying and giving some of them hope. The weapons would get a complete overhaul and would all be very different from one another.
