THE last thing you notice about Prizzi's Honor is that the credits at the end of the film roll by too fast for you to catch the names of any of the actors except the two main stars.

This is too bad, as this movie features some of the best acting to come around this year. A remarkably good supporting cast complements the fine performances by stars Jack Nicholson and Kathleen Turner.

Unfortunately, the film itself, though it features some of the funnier lines of the year, does not rate as highly as many of the performances. Prizzi's Honor is one of the best films of 1985, but this is only because there haven't been many good movies released this year. The acting is top-notch, despite some flawed Italian accents, but the movie is too long and too complicated for it to be considered a great.

John Huston has done some wonderful directing of Richard Condon's script, but try as the famed director may, he cannot overcome an overly tangled plot. Condon's two-hour-and-15-minute screenplay confuses everybody until the end, when Condon simplifies matters only by killing most of the cast.

Nicholson stars as Charlie Partanna, a stereotypical middle-aged. Italian man who has the habit of slipping a ten-dollar bill into the hands of anybody doing him a favor (he even tells a maid over the phone that he will send her ten bucks for all her trouble).

The film opens with Charlie at the church wedding or Dominic Prizzi's daughter. Charlie (who is as bored with the wedding as the audience is with the movie's slow start) quickly loses interest in the ceremony and concentrates on the gorgeous Irene Walker (Turner) sitting in the balcony behind him. As you might expect, these two will meet again.

In fact, they do, at the reception, where Charlie coolly asks her to dance. But before she can introduce herself to him, a phone call draws her away, and she never returns to the reception.

That night, Charlie gets a call from Irene, who had high-tailed it from the New York wedding reception to California. Twelve hours later Charlie, too, has made the trans-continental voyage. Under the California sun we see Charlie--proudly sporting a hideous yellow blazer stop a black turtleneck shirt--and Irene eating lunch in L.A. Not surprisingly, he soon proposes marriage, and they decide that the song playing the background will be their song.

At this point the confusion starts. In the next hour, Don Prizzi, the decrepit "Godfather" of the Prizzi family orders Charlie to kill Marxy Heller, a gangster who has cheated the Prizzi family out of a six-figure sum. After killing Heller, Charlie finds that the gambler is also Irene's husband. Finally, Charlie learns that the reason for Irene's visit to New York was to do some killing for the Prizzi family. Irene it seems, has loyalties only to herself.

By this time, twists of plot have left Charlie just as confused as the audience. "Do what, do I ice her, do I marry her?" he asks in all earnestness. After disposing of Heller, he does end up marrying Irene, causing even more confusion.

WE LATER FIND that you can only trust a Prizzi as far as the distance between the rosary beads they hold in one hand and the 45 they carry in the other.

The confusion mounts during the second half of the movie, in which killing after killing jars any viewers the movie's beginning may have put to sleep. Dominic Prizzi contracts Irene (whom he doesn't know is Charlie's wife) to kill Charlie, with whom he has a jealous rivalry. Don Prizzi tells his godson that he wants him to take over the family. The Don rids to the family of Dominic by shipping him-off to Las Vegas with a set of sterling golf clubs. Charlie decides to kill Dominic, just to make sure it's not a trap.

In order to take over the Prizzi family, though. Charlie must cover up one of Irene's boo-boo's--an unintentional murder in a kidnaping/killing job they did together. Unfortunately for both of them, this also means covering up Irene (with six feet of dirt). Irene is no dummy, though, and quickly understands that her mate is out for her life.

The showdown that emerges between husband and wife, however, is disappointing. In addition to the dismal aura it casts over the film, the scene is ruined by slow motion and by the fact that the gruesome result are shown on camera.

The film is also marred by the oh-too-familiar portrayal of the Italian Prizzi family, although an actor whose name could not be wonderfully portrays Don Prizzi killed them for the speeding credits) as a living, breathing corpse. The wives killed them for the honor of the family), except for Dominic's obsequious Annamae Prizzi, who hands him his paste on silver platter and then returns to domestic work.

Only MacRose Prizzi (portrayed marvelously by Anjelica Huston, the director's daughter) has real spunk. As the bastard of the family, her father for her loose sexuality exiled MacRose. She and Charlie had been an item for years before an argument sent her to Mexico. When she returns to the family, it is to get Charlie back--her self-proclaimed raison d'etre.

This mission is the subplot of the whole movie. But with all the killing going on, and all the tangled webs weaved by the gun-toting characters, it seems to get lost. In fact, you don't realize what MacRose is doing until about 20 minutes after you leave the theater.

In fact, that's the problem with Prizzi's Honor as a whole. Unless you can understand exactly what is happening, it seems like a lot of killing and a lot of people owing each other a lot of different amounts of money. If you don't mind waiting until after the movie to decide whether you liked it, see Prizzi's Honor. You certainly won't have time to make up your mind during the credits.