http://revach.net/article.php?id=2285

Section:  Avodah   Category: Perek Shira
Perek Shira: What Is Gehinom Singing About?
The mystery of the world is, why do some people have it so good and some live miserable lives?  All the studies in the world cannot find a correlation to properly solve this enigma.  Hashem is infinitely wise and we can’t begin to fathom how he runs the world.  Chazal however reveal to us, every now and then, little nuggets of wisdom that tell us something about how Hashem runs the world.

Koheles tells us (5:12) “Oisher Shomur L’B’Alav L’Ra’asoi” wealth is saved for its owner, for his detriment. The Baalei Mussar say that when someone has it good he should start worrying.  Maybe, just maybe Hashem is rewarding him in this world for a Mitzva he did in order to finish off his reward so that he can punish him in the next world.  Anytime you have it very good you should wonder what you are giving up in the eternal world for this passing earthly pleasure.

With this the Shiras Ariel (Rav Ariel Hodaya) explains the song of Gehinom.  “Ki Hisbiya Nefesh Shokeika, V’Nefesh R’eiva Milei Tov”, for he satisfies the longing soul, and fills the hungry soul with goodness.  This means Hashem satisfies the material desires of the wicked by rewarding them in this world for the good they have done.  Why is this something for Gehinom to sing about?  Because after this "wonderful" life, the person’s next destination is an extended stay at the Gehinom Inn.