|Lining up the shot|
Graphically speaking, XCOM: Enemy Unknown is good but not great. You will find washed out textures, but there are mods to address this. This is due to being ported from a console. Despite the washed out appearance, I was rarely distracted by it. Pre-rendered cut scenes are common. Most story elements are handled this way.
Audio overall is good. Music, voice acting, and sound effects are well done. You'll learn to recognize enemies based on their sounds and you'll relish the sound of a sniper rifle when it scores a critical hit.
Game-play and replayability are both well intact. Generated battlefields, a multitude of difficulty settings and many mods, you will be able to keep coming back. I do recommend naming the soldiers after people you know at first. I have found this draws me in further. Additionally it is fun to see a good friend then next day and explain to them how narrowly they escaped death, or completely missed an easy shot from 5 feet away and died horribly as a result. You can also use the The PC Gamer Character Name Repository that was started by Evan Lahti.
XCOM: Enemy Unknown is a solid title and I enjoyed it thoroughly. Cheskitech recommended.
For our console brethren, Xbox 360 and PS3 versions are available.