Was Stalin ever the target of an assassination attempt? If yes, why was he targeted so few times as opposed to someone like Hitler, who had multiple attempts made on his life?

Not an answer, but a question about your question.

Why compare how many times he has been targeted to someone else when you don't know if he has been targeted or how many times? Your question has a large assumption in it.

A partial answer to your question: There was a Japanese/German attempt in 1939 and there is the more famous Operation Zepplin in 1944. There are also a lot of reported but unconfirmed attempts such as a conspiracy by Nestor Lakoba (President of Abkhaz) in 1933 and there was an attempt in 1935 near Gagry by local communist officials.

It is hard to say how many attempts never took off due to circumstances, or how many were swept under the rug either by people afraid of divulging it to Stalin or by Stalin himself for the sake of appearances.

EDIT: Funny how these things work, but I popped off of reddit after this comment to do some reading, I am currently going over "MI6: The History of the Secret Intelligence Service 1909-1949" by Keith Jeffery (which is both dull and entertaining at the same time). Three pages from where I took up the book again I started reading about a 1918 plot by the SIS to have Stalin assassinated. So...there you go.