I wouldn't say that Vertigo is a great movie, especially not a great Alfred Hitchcock film. There are at least three others and probably more Hitchcock movies that are better. North by Northwest my favorite, Rear Window and To Catch a Thief and I'm sure others are definitely better than Vertigo. Vertigo is not Kim Novak's best movie either. But Kim Novak and Jimmy Stewart made Vertigo a very good and entertaining movie almost by themselves by how they worked together and the chemistry they had.
Vertigo does have a very good plot. Jimmy Stewart plays a former San Francisco police detective who is now in semi-retirement. His old buddy from I believe college gets a hold of him with a job for him, but now as a private detective. His old friend who hasn't seen a long time is a very wealthy San Francisco businessman who has a gorgeous baby-face goddess of a wife in Kim Novak. He wants Stewart to believe that his wife is going crazy and wants her to tail her to see what she does during the day.
What Stewart's character isn't aware of is that this couple is using him and is in on a murder plot. They want Scottie played by Stewart to think that Madeline played by Kim Novak is dead. When the fact is she is alive and well and comes back in the movie playing another character that just happens to meet Scottie. And Scottie is blown away by her because of the incredible resemblance and falls in lover with the same women again. A very interesting and good movie, but certainly not the best Hitchcock movie.