The Sistine Chapel is breathtakingly beautiful. Pictures of the place don't really do it justice (though artbook photos will let you see details you can't possibly glimpse when you go through).
Michelangelo's masterpieces in the Chapel -- which, if you've seen work taken from Pompeii or Herculaneum, you'll quickly realize were influenced by ancient Roman art -- very well demonstrates the painter's genius. The masterful work of the other Renaissance artists who did the Chapel's walls looks stiff and lifeless next to his.
Eve, the mother of mankind, is at the center of the ceiling. When the ceiling was first unveiled, a couple of the old cardinals were aghast and enraged that a naked woman was the centerpiece of their ceiling. They actually demanded that the ceiling be torn down. Fortunately, the others were a bit more enlightened, and the ceiling was left unmolested.
If you decide to visit the Chapel while you're in Rome, be aware that it's likely to be very crowded, and you might only have 20 minutes or so to gaze up in wonder. However, in my opinion the wait and crowding is entirely worth the experience.
Also, before you leave, take a moment to look down. The floor displays some truly excellent tilework. Some now-nameless artisan poured his heart and soul and probably many years of his life into creating that floor, and it is walked on by millions who never notice it.