Just because it does not enterain you, does not mean its not entertaining to some. In fact tv ratings suggest that the OT marathon is entertaining to enough people to continue with it (look them up before you spout bs). This premise that everyone likes the same things as you has led you to false conclusions. You can go watch a dog show or whatever you enjoy while the rest of us enjoy the final event of the olympics.
I think every nation should be allowed 10 athletes in the olympic marathon with the cut off being 3 hours for women and 2 hrs 40 mins for men. A field size of even 3000 is not too large. Sure only 20 people would even be in the race, but we could generate some interest in developing nations outside east Africa, bringing even more excitement to the event.