Greenstein has appeared in each of the first three series of Poker Superstars Invitational Tournament and all seven seasons of the GSN series "High Stakes Poker". He has also appeared in the first three seasons of the late night series "Poker After Dark" on NBC. Greenstein has also won two World Poker Tour (WPT) titles: the Fifth Annual Jack Binion World Poker Open ($1,278,370), and 2006 WPT Invitational at the Commerce Casino ($100,000). He has also won two other WPT titles in special events: WPT Father and Sons Tournament, 2006 World Poker Finals; and WPT Poker by the Book: Chapter 2. As of 2008, he began donating his net winnings to charity. At the 2008 World Series of Poker (WSOP), Greenstein cashed in six events for a total of $768,461. He also finished second in the 2008 WSOP Player of the Year standings, behind Erick Lindgren. In 2011, Greenstein cashed five times at the World Series of Poker, including a 3rd place in the $10,000 Limit Hold'em Championship for $169,512 and a 15th place in the $50,000 Player's Championship.