Even still, I know the history of the two forms and they are very distinct. So, even if I never saw the original, I would be scratching my head, trying to figure it out the entire length of the movie.
More importantly, what I would be comparing about the two films is not just nostalgic feelings. There are several dynamics inherent in the story which they fail to carry over. In the original, the Cobra sensei is a caucasian which has taken the most negative values of Japanese warrior culture and magnified them. It is a man of Japanese descent which understands the full nature of said culture and wishes to create in Ralph Machio's character an American generation of full understanding. In the new movie, it's a Chinese guy who's being a jerk and a Chinese guy who's being good. No real cultural lesson.
And the first movie had an amazingly intimate moment concerning Mr. Miyagi's tragic past, which even if they manage to do something similar in this movie, I can't help but think that, as much as I love Chan's movies, he's no Mr. Miyagi when it comes to acting outside of the action.
Just my two cents.