I love Bob Dylan, I enjoy the way he plays but Bob Dylan is not a great Guitar player, and not even a good harmonica player. He gets the job done, it all fits and there is no denying the lyrics or the power his music had on people.
The first thing you need to understand is that no one blows their brains out because they "feel misunderstood" that's like saying someone dies from sneezing. It's a symptom, Cobain was suffering from a disease and not being treated. He was an addict, his addiction caused severe depression, distortion of reality and ultimately his death. To chalk it up to merely a bad or cowardly decision shows a gross misunderstanding of his condition.
I tend to agree with your opinion on their musical catalog, I like In Utero is a very good album and Nevermind is above average, but I tend to think the circumstances of Cobain's death have elevated the band's status. Much like the status of Hendrix, Joplin, The Doors, Tu-Pac and others who meet unfortunate and untimely enRAB.
Second Buddy Holly was like 20 when he died, maybe a bit older but nowhere near 27.
I would say Aerosmith are clever songwriters and talented sure, but I don't know that they wrote too many great songs. A lot of music I like but tire of quickly. What would you say to that?