If you're reading this far I assume you couldn't give a shit about spoilers but for the record, spoiler alert.
First, anyone looking for the "right" interpretation is going to be looking for a long time. There is no right answer. Just like a dream, the movie means what you want it to mean. Like an MC Escher picture, it's a never ending mind fuck that has no answer. Reality is what the viewer wants it to be.
My interpretation is that Cobb is a man flying home from a trip and has fallen asleep and dreaming. He's missed his kids. He's a single father who's lost his wife. His misses her.
All of the characters in the movie (his dream) are people he's seen on his flight or people in his life. His flight lands, he wakes up. He walks through baggage claim and we notice that all of the characters in the movie we just watched are nothing more than passengers on his flight getting their luggage.
He goes home, spins a top on the table and sees his kids. The top is just a top. Maybe one his kids' toys he keeps as a memento while he's away. Maybe one of the kids put it in his luggage before he left.
As Freud said, "Sometimes a cigar is just a cigar". It's fun to dig deep and analyze the simplest of things for deeper meaning but sometimes a cigar is just a cigar. Sometimes a top is just a top.