Yes but what do you think sir?
I think that the Great Man Theory is not only a bad methodology for analysing history, but is also a methodological flaw unto itself:
If you actually read the works of the GMT proponents, you'll see that they don't really think that great men are central to historical events, but rather that great men are central to historical works (in the sense of books, articles, films, series, cartoons, etc) about these events.
Once you see this, you realise that the GMT is really misplaced on history when it should be placed on secondary historical discourses. The theory that
historical works have traditionally been about 'great men' is definitely a valid arguments, and one hard to argue against.
I personally see the above as the biggest strike to the theory itself, although other arguments - namely that GMT simplifies history to easily-understandable characters and events - is also valid.