Ace Combat: Assault Horizon
puts you in the shoes of a seasoned fighter pilot, going on various missions around the world. Occasional cut scenes flesh out the characters around you, but for the most part, this story isn't heavy on character development (although your character does struggle with his own personal demons and nightmares).
Ace Combat: Assault Horizon doesn't have much to offer in the way of gameplay variety, but hey, it's something of a flight simulator. You're not going to be able to do very much other than get into dogfights and look at the sky. There is some variety in the vehicles, upgrades, and multiple special weapon options. Sometimes you're a gunner on a helicopter as well. But really, you've got to love flight fighting sims to absolutely fall in love with this game.
Online gameplay options give you plenty to do when you've mastered the basics of fighting the computer opponents. Deathmatch, for example, is a chaotic free for all, that I happened to be terrible at, but there's plenty here for the seasoned flight veteran. There's also a couple of variations on defending and destroying bases called Domination and Capital Conquest. There are plenty of goals you can tweak in a game to make it a unique challenge as well. You can also adjust your weaponry and vehicle abilities to give yourself an edge as you progress. For those that want a little more cooperation and harmony, there are also some Co-Op missions that you can bring in a friend for.