Bigger sin is 2+2'er not watching Rounders. This has nothing to do with which movie is better. Like it or not, Rounders played a huge role in us all making quite a bit of money - for some of us it inspired us to play and learn, and if not it inspired the fish to play against us, not learn, and lose.
It's also a modern "channel-flipping classic" - a movie you always stop at when it's on. Other such movies are Goonies and Back to the Future. The Sports Guy wrote a very long article about the 2001-2002 NBA season comparing it to Rounders. My favorite is "Always leave yourself outs" being related to the Knicks clogging up cap room for years to come.
http://proxy.espn.go.com/espn/page2/...simmons/020411
Who the [censored] cares if a regular guy in his 20's hasn't seen Pulp Fiction? Obviously if you're a big Tarantino fan and haven't seen it you're an idiot, but other than that it's not that big a deal. There are plenty of people our age who haven't seen The Godfather, The Graduate, Clockwork Orange, Casablanca, Gone With the Wind, Sunset Boulevard, Chinatown, Dr. Strangelove, Man With No Name trilogy, etc.
Those are all better movies than Pulp Fiction, but it's not "sinful" for a 20 year old to not have seen them. A 20 year old serious poker player who hasn't seen Rounders though is the equivalent of a professional boxer who hasn't seen Rocky.