In terms of purely acting and content perspective i like the following films of Amrish Puri
Aakrosh (1980)- This is the first film which I saw in childhood where I saw Amrish Puri in a positive role that too in an art film. It opened my horizon to his acting range. The film won 6 filmfares and 1 National award.
Ardh Satya (1983)- Another National award winning movie with exemplary performances by both the Puris (Om and Amrish). Very hard hitting and realistic cop movie with Amrish playing a sadistic and machoistic and egotistic father who makes you hate him without him being outrightly villainous.
Party (1984)- A very subdued performance by Amrish Puri in a film based on a play and situated in a single night story. Even though I don't always agree with the ideology of the film it provides fodder for thought to the viewers. Meant for intellectual stimulation rather than entertainment.
Mr. India (1987)- One of the most popular performances of Amrish Puri where he played a Hitleresque character with lines like Mogambo Khush Hua and Hail Mogambo. The role could have been caricaturish in the hand of a lesser actor.
Gardish (1993)- One of his best and most emotional performance along with Jackie Shroff. Remake of National awards winning Malyalam film Kireedam, Gardish is a very strong dramatic film where Amrish Puri plays a police constable who want to see his son join forces as an officer. The scenes between him and Jackie are the highlight of the film.
Ghatak (1996)- Another dramatic role of Amrish Puri particularly his scene before his death in the film are emotional. He provides emotional anchor to the film. He won a filmfare award for best supporting actor for the film
Viraasat (1997)- He was in the film for about 40–45 minutes and by the end of the film he is the character who stays with you. Such mesmerizing performance by Amrish Puri. He overshdowed everyone in the film. Remake of National award winning Thevar Magan, Amrish Puri played the role played by Shivaji Ganeshan, and he won a filmfare best supporting actor award for the film.
Suraj ka Saatvan Ghoda (1992)- Negative role but not typical one, his performance adds a lots of layers and nuances to the film and character. He won 2 international awards for best actor for this film. Very underrated film
Damini (1993)- Who can forget the Dhai Kilo ka haath of Sunny Paji. But it was possible because the opponent was equally strong. One of the best courtroom dramas with career best performances by Sunny and Meenakshi Seshadri. Amrish Puri plays the perfect spoilsport in the film.
Chachi 420 (1997)- it was so refreshing to see him do delightful comedy in the film which he is not generally associated with. His performance and his chemistry with his secretary Om Puri is hilarious.
Honourable mentions: Meri Jung (1985) (liked his performance very much but didn't like the film), Dilwale Dulhaniya le jayenge (1995) (one of the memorable father roles he did I like him very much in such roles especially in mid films like Mohabbat (1985) , Gadar ek Prem Katha (2001) (a bit melodramatic but effective)