If you have a PC or PS4, there aren't too many interesting exclusives to get on XB1. Otherwise, knock yourself out on multi-plat titles like MGSV, Witcher 3 and the upcoming Fallout 4 and Just Cause 3.
Otherwise the only exclusives I can think of are Forza, Rare Replay, Halo: MCC and Halo 5. Forza is a racing game, not appealing to everyone. Rare Replay is a bunch of old games on one disc, only worth it if one really likes those games. Halo MCC is pointless if one owns the games on XB360, the online remains terrible, but it's good for people who haven't played those games before. Halo 5 has just released, but it has had to make a good many compromises to run at fixed 60FPS. Most notable is the complete lack of splitscreen, no more couch co-op and the graphics have
horrendous pop-in. Impressions are mixed. Wait for the dust to settle and check the reviews before buying.
The Master Chief Collection and then Halo 5.
Basically the exclusives. If you haven't played Titanfall yet I suggest giving it a go. Some great upcoming games such as Halo Wars 2/Gears of War 4.
There's another suggestion in GoW4. Maybe pick up the GoW Ultimate Edition if you're a big Gears fan or you've never played the first game, though this is a game also coming to PC.
Halo Wars 2 also comes to PC and I don't mean to be horrible, but it's pointless on console. A traditional style RTS plays horribly with a traditional controller, as much as I liked RTS and Halo, I never bought the first Halo Wars since it was a 360 exclusive. For example, I even tried out the different control methods in Pikmin 3, the traditional controls using the WiiU Pro controller were terrible and the game was only really playable with the Wiimote&Nunchuck, since it's the closest thing to a mouse&KB on console.
Overall, there isn't much to get if one also has a PC or PS4. But if the XB1 is your only console, you'll find a lot of great games to play. Since I have a PC and a PS4, I currently have no reason to buy an XB1. I eagerly await a reason for me to buy one. IMO, one shouldn't buy a new console unless they know what they'll be playing on it. But I can't talk, I've bought a PS4 that I've yet to use or buy an exclusive for. So I'm essentially in the same boat as the OP.
