Some of you ancient gamers may remember X-COM. Turn-based, squad-based, tactical goodness. I still recall the fun of tossing an alien grenade into a house just to see how many walls I could blow out. (“Sorry about your house ma’am. Just doing our job.”) Sadly the series went South with X-COM Apocalypse when the developers decided they had to jump on the real-time strategy bandwagon. It wasn’t the worst implementation of RTS that should have been turn-based, (That honor belongs to Star Wars Rebellion in my opinion.), but now Firaxis is rebooting the series with a face-lift, some reimaginings, while (as far as I can tell) remaining true to the spirit of the original. Here is a good history of the series:
Most appealing to me, is that you get the same game whether on the PC or a gaming platform (minus the modability).
Now, if you really insist on reliving the old days other than booting up the original, try Xenonauts.

True to the spirit of the original in some senses only, their reboot revamped the series into a gritty “M”rated title.
*Sigh* I so do get tired of “M” worshipping gamers and developers. I’m not against there being “M” rated games, but c’mon, when older series have to garner “M” ratings just to get an audience (at least in theory), thats pretty pathetic.
Just look at next years new Tomb Raider title, a gritty Tomb Raider reboot, are you kidding me? Or, believe it or not, a “M” rated Star Wars game. A Star Wars game for crying out loud! How retarded is that?
God I miss the old days when games got an “m” rating for being a little too bloody, not today’s torture porn violence/gore, foul langauge, and hyper sexuality.
I got the game and played it pretty extensively and can’t really figure out what it got a M for. A squaddie will say “dammit!” on a missed shot, deaths are somewhat violent but nothing outrageous. Frankly, I’d almost let my 9-yr old play it.
Never played it, only know what I read from the reviews, and they described it as a gritty reboot, which the series moving up from a “T” rating to an “M” rating would indicate anyway.
As for what it got an “M” rating for, here is the link to the ESRB website:
http://www.esrb.org/ratings/synopsis.jsp?Certificate=32310&Title=X-COM%3A%20Enemy%20Unknown&searchkeyword=X%20COM%20Enemy%20Unknown
They give pretty extensive content descriptions there, as they do on commonsensemedia.com
http://www.commonsensemedia.org/game-reviews/xcom-enemy-unknown
So I would advise against letting your kids play it.
FWIW, ESRB ratings are pretty accurate these days, if it says it’s rated for something, it’s probably there…but with coding being so extensive, everynow and then you get a “Hot Coffee” moment, sadly.