Outside of the Mob, Gotti did leave a huge lasting legacy. For a lot of young street guys all over the world the name Gotti has basically become synonymous with the word mobster. He is a brand, there's no denying that.

Within the Mob...it's clear to see that his way of handling business as a boss did some damage to the Gambino's and to the American LCN as a whole. He did have a huge ego and him loving the camera definitely turned him into a target for LE.

Now there's no denying that Gotti when he was around came from a very respected crew and had a TON of backing. I also get the impression that when he was boss and even before that, he was generally well liked by quite a lot of fellow mobsters as well as quite a lot of civilians.

One thing you can say about Gotti is that he was loyal to his friends and to Cosa Nostra. He did have a huge ego, but he wasn't an entirely self-serving asshole.
Gravano, Casso, Amuso, Massino...were all entirely self-serving psychopaths. Can you make the same case for John Gotti? I don't think so. Compared to most bad bosses, Gotti was a man of principle. He wasn't the greatest boss, but he wasn't the worst either.