I've run two marathons. My first marathon (Canadian International in Toronto Canada), I completed on a dare from my buddies. I had never run more than 1 mile in my life but after sitting at lunch with my runner friends who said I could never run a marathon scheduled for 2 months out, I took them up on it. I trained starting the next day for 6 weeks, gradually increasing my distance each week without pushing to hard to avoid injury. I managed my long run of 18 miles 2 weeks before my marathon and then tapered until race day. I completed the marathon running all the way, albeit slowly after mile 20. My buddies owed me lunch.
While living in Boston, I raised money for a local charity to enable me to run in the Boston Marathon. I wanted to train more throughly than Marathon #1 and finish under 4 hours. I trained too hard and injured myself. While I completed the marathon and ran faster than my first marathon, I was not satisfied.
I now want to qualify for Boston which means a time in a qualifying race of 3:30 or better (for my age bracket). The maximum distance I have run at this speed (roughly 7:45 per mile) is a 5K. I have a lot of training to do.
Running a marathon is very satisfying for me. Obviously, the training provides benefits:
Keeps me in shape and I feel good;
Keeps my energy level up high all day;
Gives me more latitude in what I eat (healthy food of course but greater ability to stray come dessert time);
Running the marathon produces a different set of benefits:
Satisfaction of completion;
Running with a bunch of other like minded people who pull for you during the run;
Opportunity to see a different city / region;
Sense of accomplishment.
For me, the pride element only enters when I surpass a race goal. Not reaching the goal does not diminish the satisfaction of completing the marathon, but I do have a sense of pride by putting an aggressive target out there and surpassing it.