every single review I have read of it has not exactly been favorable
gratuitously violent
This is quiet baffling, the dollar films have about 6 times the body count this film has. The only thing that surprised me as far as violence was concerned was the bloodshed (this probably being the only film where Leone uses blood squibs). In the case of this movie, it is by no means gratuitous violence, it's
realistic violence. A bullet to the head is not a pretty sight and Leone shows that. The problem is today everyone has become all too comfortable with violence, failing to see that ALL violence is gratuitous, be it real or fictional.
no likeable characters
well of course they aren't likable, they're mobsters. Ever since the godfather people have looked at mob movies as though they are about these swell guys who are constantly harassed by the evil policemen (how dare they enforce the law!). Personally, i like the characters in this film and in some cases identify heavily with them. I feel that they are quite likeable, but it is their actions that are unforgivable.
horrible pacing
Only to someone who doesn't bother to invest himself in the film. When i watched it I never felt that it dragged or rushed, it was as though there was a complete and unbreakable bond between the sights and sounds of the TV to my head. The only time i was ever out of it was when i had to change disks to complete the movie (coming in at an awkward time).
infamous rape scene
I'll level with you and say that is a very uncomfortable scene, but then again, when is rape ever comfortable? A lot of people want the scene to be shortend (or deleted) because of their discomfort with it, but like the violence, the film shows rape as it really is, hideous.
confusing chronology
i don't know where this comes from. anyone who really pays attention to the film should understand the chronology of it. Certain things trigger Noodles to flashback to his childhood and vice versa. If anything should be confusing, it's the ending. Although it shouldn't frustrate you, its only there to make you think.
So why does this movie fair so poorly with critics and audiences?
That depends, who are these critics, because these don't sound like any critic reviews I've ever read on the film. Remember, the Oily psuedo-intellects with acne problems known as IMDB members don't constitute as actual critics.
if you want to here some actual critic and audience responses read this bit from wikipedia.
The film's premiere at the Cannes Film Festival was an astounding success. Though some female audience members were offended by the rape scenes and depiction of women (Leone was often accused of misogyny based on his films' portrayal of women., the film was extremely successful, garnering a fifteen-minute standing ovation from the audience. The uncut European version of the film won rave reviews, and was very successful throughout Europe and abroad. However, several sneak premieres in Canada and the US gained a mixed reception at best (some suspect due to studio tampering). The film was drastically edited, as mentioned above, more for commercial reasons than anything else. Leone, who had turned down an offer to make The Godfather twelve years earlier, was indignant when several American critics compared the butchered version of his film to "a Jewish Godfather". The 144-minute version was a huge flop and American critics destroyed it. Roger Ebert wrote in a 1984 review that the original cut was a masterpiece but the American theatrical cut was a travesty.
The uncut version of the film gained widespread critical acclaim and a large following. James Woods, who considers Once Upon a Time in America Leone's finest work, mentions in the DVD commentary that one critic dubbed the film the worst of 1984, only to see the original cut years later and call it the best of the 1980s. Ebert, in his review of Brian DePalma's The Untouchables, called the original uncut version of Once Upon a Time in America the best film depicting the Prohibition era.[2] Sight and Sound magazine placed it among the ten best films of the last 25 years when it attempted to do a poll on recent films.Am I wrong to trust the critics? Because I do.
Critics should never decide what you can and can't watch. You are the best critic in what you do or do not like, not anyone else.
How can it be so colossally different than all the rest?
Well it is a movie about the jewish mafia, while all his others are western, But other then that it still has the same Leone style and pacing that we have come to know and love. If you like his other movies there's no reason you shouldn't like this one as well