That depends on which ending you're talking about: real time or screen time?
The chronological ending is Butch driving off into the sunset (in a manner of speaking) with Fabienne on Grace, his new bike which is definitely a chopper, not a motorcycle. It's a pretty standard movie ending. The hero boxer defeats the evil guys and saves the damsel in distress who then blows off one of the villain's crotches with a shotgun.
Okay, maybe it's not that standard, but we've reached the finale of Butch's story and with him and Marsellus "cool" we get a sense of completion. It's how a typical literal-minded director might have closed out the film.
But, as you know by now, Quentin is quite opposite of typical. Instead, the movie ends about midway through its chronological order, but that doesn't mean it simply cuts the story arc in half. In case you missed those black screens with the white words on them, Pulp Fiction is broken up into multiple parts. It's more of an episodic story with the episodes out of order than a randomly sliced up single narrative.
So the last scene of the film is actually a continuation of the first, the ending of Vincent and Jules' crazy day that finds them in a diner being held up by Ringo and Yolanda. This is the true climax of the film, as Jules is forced to confront his past life and change his violent ways in dealing with these lowlife criminals. Maybe you think that a scene in which no one gets shot or dies or anything is hardly climactic in a film which already has so many dramatic scenes. But it's not about action, it's about the heart of the story.
This ending is the thematic center of Pulp Fiction—redemption—and the reason why Tarantino finished the film with it instead of some cliché scene of Butch and his happy ending.