The glue that holds this all together is this great design behind having you constantly balancing your short and long term goals. In the end you need to fight off the alien invasion, but you're not going to be able to save everyone. If you spend all your funding on upgrading your soldiers, you can certainly do better in missions, but if you ignore your satellite coverage, panic will quickly rise to unmanageable levels and nations will start to leave. You'll need to make some tough decisions, especially on the harder difficulty settings. Do you abandon one nation to focus your efforts on a smaller area or how expendable are your veteran soldiers? There are even extra incentives and decisions to consider during play, like selling off valuable alien technology. The quick influx of cash might be beneficial right now, but you could be kicking yourself down the line when you end up needing them again.
And you'll desperately want that easy money in order to pay for any number of upgrades to try and give your soldiers an edge, XCOM: Enemy Unknown is wonderfully challenging, if you want it to be. Fans of the originals will certainly want to start out in Classic difficulty, but even the Normal setting is not a pushover. The enemy AI will not absentmindedly rush into your ambushes, and is more than happy to sit back on overwatch if a better opportunity isn't present. There's also an Ironman option, which creates a single auto-saving file. This means all your decisions and actions become permanent, there's no quick loading out of losing your best soldiers. It may not be for the faint of heart, but everyone should try it at least once.
For as much fun as the game is, there are a few areas that could have been better. The multiplayer can be a fun diversion, but it feels tacked on and not very well balanced. The set-up is simple enough; each player assembles a squad that worth a specific point value based on the units and equipment, which gives you a lot of freedom to experiment. One player might prefer six relatively cheap units while another fields only two very powerful ones. The balancing issues come in from these point values. The human's advantage is supposed to be more customization, but the aliens are much cheaper for getting units with roughly equivalent capabilities. Also, a few of the powers like mind control can essentially instantly end a match. A cooperative-based multiplayer feels like it could have been a better fit.
Another concern is the potential for the game to feel stagnant over extended play sessions or repeated playthroughs. The occasional terror or council missions, which ask you to rescue VIPs or civilians, can help to break up the monotony but, ultimately, most of the missions are to search out and kill all the aliens. And you'll do them again and again. You might find yourself hoping no missions pop up just so you can get on with your next research goal or funding influx and continue on with your plans. This is further aggravated by how often you'll see the same or similar maps. In XCOM: Enemy Unknown, mission locations and enemy placement are randomized, but the map layouts are not, so you can find yourself feeling like you're running the exact same assault plan on the exact same downed UFO.
Ultimately, these issues might dampen the experience, but on the whole the game is a fantastic. While many games stop at the decision of what weapon to equip, XCOM: Enemy Unknown forces you to make some hard choices both on a global scale and while combating the aliens.
Bottom line: XCOM: Enemy Unknown will have you swapping horror stories at the watercooler, and loving almost every minute of it.
Recommendation: Grab XCOM: Enemy Unknown if you're a fan of the original series, it lives up well to the XCOM name. New fans will be drawn in by the tactical gameplay and the enjoyment of overcoming a challenging game.
This review is based on the Xbox 360 version of the game.