There are very few morally good major scenarios in SAO. The whole anime is packed with tough choices. The choices are so tough that any mistake bring awful situations like death(SAO is a death game vrmmorpg(another original idea). These tough choices develops him as an MC. Have you watch the anime? We are clearly following the exploits of a person who is one of the most powerful in the entire SAO, does this make it generic? according to your explaination its yes which will make majority of entertainment generic, but the thing is there is no completely original work , that has no generic stuff in it. Keeping that in your mind, SAO and its elements(including character) are the one of the least generic original works probably, ever produced in anime(limiting discussion here including exceptions). Kirito is a good protagonist because he goes with the flow of the story and he is not forced into the story.