Blade Runner is a classic, and is certainly Ridley Scott's best film. But if you're expecting nonstop action tailored to MTV-era attention spans, you're looking in the wrong place. It's a moody, philosophical film noir set in the future, a layered, thought-provoking piece that challenges the viewer and demands multiple viewings. And it's one of the most visually and stylistically influential films in science fiction cinema; its footprints are all over the cultural landscape.
That said, I didn't enjoy the theatrical cut. It wasn't until I finally saw a version without the plodding voiceover that I understood what the film was really about. I think the narration dumbed it down and even changed the meaning of some very important things about the story.
As for the OP's question of why there are so many versions, it's because, as is so often the case in US cinema, the version of the film finally released to theaters was not the one the director wanted. IIRC, the company that put up the completion bond on the film (which went way over schedule and budget) kind of took control of its final editing, or else it was the studio. So we got the voiceovers to "clarify" the story and we got a tighter cut and we got the imposed, thoroughly illogical "happy ending" tacked on. But years later, film scholars and fans discovered an early workprint that was closer to the original intent, and it became well-regarded and somewhat legendary. Additionally there was the network television version with a number of scenes restored, and the international version with some other differences. So there was a growing interest in seeing the film as it was meant to be seen. Eventually we got the "Director's Cut," which wasn't literally that but was pretty close. Now the "Final Cut" really is Scott's personally overseen restoration of the film, not only recutting it the way he wanted but using digital technology to fix some of the production errors (most notably replacing the face of an obvious stuntwoman in a bad wig with the real Joanna Cassidy's face).
So if you only want to see one version of the film, the Final Cut is probably the way to go. The rest are worth tracking down if you're interested enough in the process to explore the variations, but that's more for devoted fans or film students.
