i ve some different views my friend...i read the epic and i find some another views..
arjuna karna and pitamaha all were great warriors...but lord chose arjun for some reasons...
arjuna defeated karna and pitamah many times...remember virat judh...arjuna was alone.. but defeated kuru sena including bhisma and karna...in the war also he defeated them... 2nd day of war was arjuna's day...bhisma failed 2 stop him...at the time of killing jayadratha, karna failed 2 stop him..he defeated karna...,and the same happened at draupadi's syambar..arjuna broke karna,s dhanush
bhisma had eccayamrityu kabach...this was not right for a great warrior...shikhandi was arjuna's kabach...so he used her that time..arjuna's ban couldnot break that kabach but bhisma could not break arjuna's dhaal...palla was same and arjuna won...these words are bhisma in mahabharata
karna was a great warrior...but he went 2 a wrong path...always provoked duryadhan for war ... little bit of jealous...took part in bastraharas,,told some bad words... and aLSO BROKE RULE in killing abhimanyu...1 of the 8 warriors who killed abhimanyu was karna...so arjun also broke rule 2 kill him...
arjuna had divyastra...but in real mahabharata there wwas adiscussion of arjuna and draupadi...arjuna told that he did not use divyastra as it would harm mankind...if i used them the war would end up in 2 days but everything would destroy...he always stood for dharma...so lord also chose him for gita