Curious why you've watched them out of order or are you going chronologically with The Good and the Bad first? I don't remember the films too well, but I remember For a Few Dollars More being my favorite.
Well, I didn't actually know the chronological order for the films, but I knew that the most popular theme song that's been reused in hundreds of American comedies and shows was from
The Good, the Bad and the Ugly, so naturally I just assumed that it was the first one. I had no idea it was the third one until afterwards. I've never heard of another trilogy where the third one is generally considered to be the best among the big mass, well except for maybe the Star Wars prequels.
Usually when it comes to films, the first one is the best and sequels rarely manage to beat the original.
I've actually seen
For a Few Dollars More now as well, and I must say that is was much better than the first one. However the third is still my favorite. I'd rank them as followed:
A Fistful of Dollars: 7/10
For a Few Dollars More: 9/10
The Good, the Bad and the Ugly: 10/10