Nah, why would it? I mean, I enjoyed movies like Titanic and The Passion of the Christ (well, enjoy is not the proper verb for that one), and I think I knew how they would end.
Personally, Abre los ojos makes you fell deeper emotions.
i saw vanilla sky first but abre los ojos was much more powerful. it was just made better. even though i knew the ending, its one of those movies you can watch again and again.
and the beauty of titanic is knowing that everyone on board is doomed. its a little different than this movie.
more than likely, your experience has been ruined. for the reasons why, see my other posts on the boards here. i don't want to bore people by reposting.