Topol received his only Oscar nomination to date for portraying Tevye in Fiddler on the Roof.
Fiddler on the Roof is a musical, and certianly old fashioned in many ways, one way being the very obvious acting that often goes with a musical. After all it is pretty hard to break into song in any subtle fashion. Throughout the film there are several overacted performances, or underacted performances. I must say the overacted performances tend to work better for the musical, rather than some of the dull underacted ones. Topol portrays the center of all of these performances.
Tevye is a character that is hard to not portray in at least partially flamboyant fashion. After all he is a character who directly talks to God (the camera) in many scenes. Topol actually handles these particularly well. He is quite convincing in his character's constant questioning, telling or asking God about what is happening to him currently. Topol does in fact make this aspect of the film and Tevye's character aspect pretty natural.
Topol actually handles all the more flamboyant parts of Tevye well. Topol conveys well just the distinct enjoyment, and his distinct jovial attitude Tevye takes toward life. He really throws the right energy into the role that is perfect for Tevye, and do to the fact that he instantly sets up this manner of the character he actually makes breaking out into song for the character pretty natural, well as natural as it can be anyways.
Topol of course sings the songs well enough, but that really does not matter precisely, what I care more about is indeed how they perform the song. He always throws either the right heart or energy into his performances of the songs. I think "If I were a rich man" shows this quality the best, he just completely throws himself into the performance, which is terrific.
I won't say there is a lot of subtle moments in his performance, but he does show more of Tevye than just external colorfulness of the character. He does develop a core of the character showing his character's honest love for his family, sadness for the way the world treats him, and his reluctance to lose the Jewish tradition. It is not a lot but Topol makes sure it is there, and does weave it along with the more flamboyancy of the character. Overall Topol gives the best performance in the film because it appropriately expresses the usual aspects of a musical performance well, without being an excessively over the top performance.