I've recently encountered this saying and got confused how to interpret the message of it. I wonder if that is supposed be sarcastic or possibly proud to be greedy.
It's a spoof of the kinds of slogans you find on motivational or inspirational posters; it's an example of wry humor. Typical motivational or inspirational slogans extol important virtues to strive for to give your life meaning. This slogan does the reverse, at two levels.
It says that the most important thing in life is collecting playthings. That's a trivial life priority, but by itself, might mean having fun while you can enjoy it. But it carries it a step further -- it portrays life as a contest, where you "win" not by being fulfilled or happy while you're alive, but by being the one who dies with the most toys (you win posthumously).
And just to add, years ago, I worked in an office where many people had motivational or inspirational posters on their wall. I brought in one with this saying, so it was juxtaposed with the serious posters. People cracked up, which may say more about the warped sense of humor of the people I worked with. :-)