Nothing beats the sense of accomplishment you feel after months of aches, pains, and soreness all getting you 26 miles, hands raised as you crash through that ribbon and collapse from exhaustion yelling "I DID IT!" Right? I disagree. I feel much more accomplished when I pull 3 or more DVDs off my shelf, stack them on my entertainment center, then watch every minute of them without moving from my couch for anything other than a piss break, a beverage run, or to switch the movie out. Putting that last DVD back in alphabetical order after a 12 hour day of cinematic debauchery feels way better than going to the gym and running on a treadmill for 8 hours. Who needs muscles? Not this guy.
Sitting down with a group of really good friends for a movie marathon is the ultimate social experience for me. I'm not a partier unless it's just a bunch of people I know, and I'm a big movie person, so having a bunch of people over to watch countless movies, bad or good, is always a treat. Movie marathons have been around since the dawn of time, or at least since the dawn of the VHS tape, which started to take off at about the right time to supply one trilogy to the masses and start EVERYONE'S marathon experience right, mother fucking Star Wars.
Watching the original 3 Star Wars movies all in a row with all of your closest friends is like a right of passage. Pubes shouldn't grow on you until you've sat down, 5 or more sexually frustrated 13-years-olds, no less than 70 instances of acne among the group, making lightsaber sounds, talking like Jabba the hut, and sitting silently, pillows in every lap, watching Princess Leia in the gold bikini. You can't properly enjoy life until you can reflect on this exact experience with those same buddies 10 years later.
There's an art to it, however. Sure, grabbing 5 random movies off your shelf will still finish the job, but having a movie marathon with a mission is exponentially better. It's like buying a 5 dollar hand job versus spending $1000 on an escort for the night. McDonalds vs. Chilis burgers. You can't measure the difference. Putting in Fellowship of the Ring with the clear goal of watching the entire series will surely pay better dividends than watching 3 randoms.

Best experienced as a group but for the first time together, movie marathons give you the freedom to really get into the movies. You can quote along, cheer at your favorite scenes, point at your teary eyes and say "look how gay I am for this movie". There's bound to be trivia flying around too, creating a deeper understanding of the films you already love. Marathons are all around a great time.
In preparation for Harry Potter and the Half Blood Prince, Kristin (who is a tremendous cook by the way, which I am definitely NOT saying so she will cook me delicious food later), Wil and myself geared ourselves up for a day filled with magic and wonder. Starting off with a late breakfast to power our quest, we took the five DVD stack, laid them out, and dove in around 1pm. And at 1am, our 12 hour marathon was fulfilled and we parted ways smoking our proverbial post-coital cigarettes and fell asleep knowing we had accomplished more that day than we had in the past month, regardless of how many other movies we watched.
Movie marathons are a great way to get through a day, weekend, week off, whatever. Watching movies is our past time, and watching dozens in a row is better to me than slamming beers with a bunch of idiots and yelling about bullshit. So next time anytime someone tells you that watching all the Harry Potter movies in a row is dumb, you tell them it made you a better person, and that they're stupid, and then punch them in the face.