That first of the modern era batman movies w/jack nicholson as the joker. The commercials leading up to release - showed *everything*. I may have liked it had it not been for the commercials having shown me the entire thing in advance. I'll never know.
same w/die hard 2. Not as bad. The commercials leading up to release didn't show everything like w/the above example. But they showed the end. They showed how he kills the badguys at the end - in the commercials. I didn't realize this at first, but about halfway through the movie, I knew exactly how it was gonna end. Yeah yeah, of course everyone knew the good guy was gonna kill the bad guy at the end in the sequal to a hollywood action movie that ended that way the last time. But because of that commercial I knew what place in the world all the characters were going to end up, which told me what was going to happen from the middle of the movie on, what mistake the bad guys were going to make, and exactly how bruce willis would take advantage of it to kill the bad guys, and what his pithy remark would be while he did it, and what it would look like visually.
Not all movies do this on purpose, but its easy to make deductions from a tiny excerpt of 1 little scene in a commercial that tells ya volumes about a plot, even if you're trying not to make such deductions. Especially in movies like die hard that might be great movies, but lets face it, don't have elaborate plots.
You can never watch a movie 'for the first time' again. But its nice to be able to watch it 'for the first time' - the first time. Imagine if you had never been able to watch the Usual Suspects for the first time, that ya knew the ending, in advance, the very first time ya saw it. So, now i avoid commercials/previews. turn them off/fast-forward/skip/leave-room/fingers-in-ears, whatever i have to do, to avoid this. And I see movies as soon after release as possible. All to avoid these omnipresent commercials.