Ahem, allow me to prove you wrong:
Ryuk becomes a nefarious demonic creature who, out of boredom, creates a notebook and infuses it with some of his powers, then drops it in the human world where Light, golden boy and all around nice guy of his school with perfect grades, finds it. The first rule ("the human whose name is written in this note shall die," probably changed to "this book/notebook") is probably written somewhere prominent, but the others are noticeably lacking.
Thinking it's a joke, Light writes some famous criminal's name in the Death Note and later hears on TV that the criminal died of a heart attack. Light freaks out, and that's when Ryuk appears and explains what the Death Note is and its basic rules, but it's done in such an unclear, glossed over way that viewers are left confused as to the actual requirements of use and limitations of a Death Note.
With Ryuk now constantly whispering in his ear, goading him on to use the Death Note to "make the world a better place" because he's the only one who can, Light hesitantly starts ridding the world of its most notorious criminals while Ryuk constantly reassures him that he's doing the right thing.
Enter L, a mysterious, humorless middle-aged detective who's never seen eating sweets, famous for cracking the toughest cases. Using some vague "deductive reasoning" he starts narrowing in on a profile that matches Light's. What follows is a tragic game of cat and mouse, with the evil Ryuk pulling the strings of poor, unsuspecting and pure-hearted Light the entire time, convincing him that he's on the side of good.
Misa is introduced at some point (probably with a name change to something stupid like Mitzy) as Light's classmate and love interest, and eventually figures out what he's doing. She still supports him, but is worried about Ryuk. Eventually L puts all the pieces together and approaches Misa to help him capture Light, and he succeeds in convincing her.
At the final confrontation between L, Misa, Light, and Ryuk, Misa tries one last desperate attempt to convince Light to leave Ryuk, and just as it looks like it's working, Ryuk, in a fit of rage, pulls out his own Death Note and dramatically writes Light's name in it. Misa and L are horror-struck as Light keels over dead, and just as Ryuk starts to write their own names, Rem makes a dramatic entrance and introduces herself as Misa's demon. She then makes some speech about how she cares about Misa's wellbeing and won't allow any harm to come to her, then announces that Ryuk's been rogue long enough and his time is over, and dramatically writes his name down in her own Death Note as he stares wide-eyed in horror before writhing in agony as he dissipates into nothing.
Rem then pulls out a Death Eraser (like the one from the original unused first chapter) and picks up Ryuk's Death Note and erases Light's name, bringing him back to life. He and Misa embrace, and L comes over and welcomes him back. Things wrap up thereafter, glossing over the seriousness of Light's crimes and leaving unanswered whether or not they used the Death Eraser on all of his victims, and just generally ignoring any moral ambiguity presented in the entire movie.
Oh, and the entire cast is white-washed and the setting is somewhere in the U.S.
tl;dr Light is a wide-eyed innocent who falls under the evil demon Ryuk's influence while the middle-aged, super serious L hunts him down and convinces Misa to betray Light and help stop him. At the final confrontation Ryuk kills Light, but the twist ending is Rem showing up and killing Ryuk, then using a Death Eraser to bring Light back to life and everything ends up as happy fun times.
Have I ruined it enough for you?