I wonder whether you are referring to the end of the action of the story, with Holmes, Watson, and the others capturing Clay and his accomplice or whether you are referring to the last line of the story. Either way, I feel the ending is satisfying enough.
I do feel that the capture of the criminals is satisfying. This is largely, however, because I go into any detective story expecting that the detective will solve the mystery and capture the criminals. This ending is satisfying mainly because it fulfills my expectations. I also liked that Clay and Holmes both seem so unemotional about the whole thing. It is as if Holmes has beaten Clay at a game of chess. I like that kind of cool detachment. It reminds me of the sort of sang froid that Rudyard Kipling says is expected of men in his poem “If.” I grew up thinking that that was one standard by which men are judged and so I like the fact that both men act in this way.
I also enjoy the very ending of the story. Once again, Holmes is not making much of his triumph. Watson is somewhat effusive, telling Holmes that he is “a benefactor of the race.” Holmes brushes away the compliment. He says, if I understand the French correctly, something to the effect that the man himself is nothing, it is the work that is everything. Again, I like the fact that Holmes does not make much of himself. By ending the story in this way, Conan Doyle reveals something of Holmes’s character. The fact that I like this aspect of Holmes’s character helps to make this a satisfying ending for me.