I haven't played xcom and don't know too much about it. Is it good?
Well, depends on what you are looking for. It's a strategy + tactics game. The tactical game is TBS, you control a squad and have to clear an area of aliens (specific objective changes, but that's the basic idea); cover is your greatest friend, the fog of war is your greatest enemy. Your soldiers "level up" with kills, and you get to choose new abilities depending on their class: heavy gets the explosives, sniper can attack from far away, assault is the close combat specialist, support is the medic/jack-of-all-trades. Oh, and there's permadeath.
The strategy game sees you manage the limited resources of the program, together with what your soldiers manage to scavenge from the battlefield, to research and build new technology to help you fight the rising alien menace, while keeping the world panic under control (you lose the game when a certain number of countries descend into madness, not when all your soldiers die). The invasion, and Earth's defense, follows a storyline of sorts as you discover what exactly the aliens are looking for.
So during the tactical part, you often have to weight how much risk you are willing to take to scrunge better resources from the fight (example: killing an alien gets you its corpse and fragments of its weapon; blowing it up with missiles will only get you the corpse; stunning it with a taser will let you interrogate it and keep its weapons intact). There's also a variety of effective squad builds to keep things interesting.
The beginning of the game (say 2h) is a bit slow, but it becomes very addictive afterwards.
If you like strategy games (a la Civilization) or rpg-ish TBS games (FF tactics, Fire Emblem, etc.), I would definitely recommend it. Get it with the Enemy Within expansion, which promotes a riskier (read: more interesting) approach to the tactical fights.
