If we're talking about the '80s and '90s, there can be no real question that Apple screwed up badly. How and why are still legitimate questions, but the only reason Apple lasted until OS X was because Microsoft needed them as a token competitor. They were constantly on Death's doorstep, and I don't doubt that if MS wasn't under anti-trust watch, they could have finished Apple off then.

If we're talking 2000s, then that's a totally different story.