Why "Best Supporting Actor", for Goodfellas, when he was the star of the movie?
Good question. You are right. In fact, Liotta has De Niro beat as far as screen time, probably 2-to-1.
This is just my opinion. I am not claiming it is right or wrong. It is formed from observing how award voters nominate movies and actors for a LONG time.
Opinion: When a movie has an ensemble cast that includes a big star (De Niro) with a notable role and a
younger actor has the primary role, it hurts the young actor's chance of getting a nomination and/or winning an award if they do get nominated. Let's look at three award presenters:
Bafta Awards/
Foreign films
De Niro gets the Actor In A Leading Role nomination.
New York Film Critics Circle Awards/
Domestic films
De Niro got the nomination AND win for Best Actor.
Golden Globes/Different Voting Perspective from Oscars
Oscar Best Actor nominees Robert De Niro and Gerald Depardieu were deemed 'not as good' as Al Pacino (
The Godfather, Part III) and Robin Williams, who the voters preferred MORE than De Niro in the
same movie.
No Liotta nominations for Best Actor for these three notable awards.
Just saying. I bet Liotta would have been nominated for a Best Actor if
Goodfellas didn't have De Niro. Easily. Likewise, I believe Liotta would have gotten a Best Supporting Actor if De Niro had been in the movie for a 1/4 of its run time.
Is it fair? Heck no, but it is what it is.
https://www.nyfcc.com/awards/?awardyear=1990
https://awards.bafta.org/keyword-search?keywords=actor in a leading role&f[0]=integer_year:1991
https://www.goldenglobes.com/winners-nominees/1991