Let's be honest, though: you're in it for the multiplayer.
The lack of splitscreen play outside of Future Soldier's decent Guerilla mode (a riff on Gears of Wars' Horde mode, with tons of replay value) is a major issue for me, and the absence of co-op matchmaking is also sorely felt. But those gripes aside, this is easily the most engrossing online shooter I've played in years.
Modern Warfare's influence is felt here as well, of course. What would online play be without levels to gain and weapons to unlock? Guns are doled out piecemeal, as are attachment points used to purchase the many, many firearm modifiers. The game's much-touted "Gunsmith" allows for piece-by-piece weapon refinement, from scopes to triggers, stocks, barrels, and more. it's "gun porn" at its finest, and every shooter should have a Gunsmith mode from now on, forever. (Ignore the mode's hare-brained Kinect functionality, and unplug your Kinect if you have one, as the game periodically and rather obnoxiously prompts you to "take a break" regardless of whether you're using it.)
Classes are varied enough that you'll want to switch between them often as you ride the ever-changing tides of online battles. Scouts get active camo and sniper rifles, Engineers use sensor grenades, shotguns and airborne drones, and riflemen pack the firepower, with plenty of wiggle room to tailor each class to your particular tastes.
Most online shooters inadvertently reward lone wolves who ignore team-based objectives in favor of racking up the highest body count, but Future Soldier's greatest strength is in the ways it pushes players to work together. An assist grants as much experience as a kill, and spotting targets with a sensor or drone or stun-gunning enemies and hacking their intel gives even more points. Objectives are captured faster when your teammates are in proximity, and galavanting off alone is more than likely to get you killed.
Future Soldier encourages tactical, thoughtful gameplay, rewarding players who use their mics to coordinate strategies and communicate enemy positions. Using cover is essential, and an incredibly smart three-tiered aiming system—hip-firing, shoulder-bracing and clicking through to the scope improve accuracy by degrees—eliminates the snap-to-scope auto-aim that plagues other shooters.
The selection of maps is nicely varied, with some enhanced by variables (for example, a sandstorm) that decrease or improvement visibility and other factors. And the game modes currently available are pleasantly complex. The absence of straight team deathmatch is somewhat baffling, but the ever-evolving "Conflict" (objectives are spawned at random), higher-stakes "Siege" (you get one life per round), and familiar "Sabotage" (like Halo's "Assault") provide just enough variety.