I think the reason is because they always innovate. The McCafe thing is just brilliant, cutting down Starbucks crowd. If you are a businessman, you will just practically go to McDonalds for lunch, and have coffee there (with the availability of McCafe); than waste your time going to Starbucks to get coffee. And they are way cheaper.
And this means increase in their traffic count, and increase in their sales.
This is aside from the fact that Ronald McDonald is just plain lovable!
