I actually dig that question. I mean it’s impossible to be slop and quality, but the underlying idea of “movies that became popular because they simply were good” I like.

Movies that (at the time of the shooting) have no star actors, well-known directors and do not build on a world/lore that is already well established with a big fan base (like LOTR). Movies that are just good because the work is phenomenal and nobody who walked into the movie when it came out could have predicted this.

It’s okay when people became stars because of that movie, but only if the movie was liked before they became stars. It’s also okay if the genre was already popular, I don’t think there’s ways around that for many movies given the limited number of genres.

For me this is Rashomon, the movie that (later) catapulted Akira Kurosawa and Toshiro Mifune into stardom, It is now considered one of the greatest films ever made and among the most influential movies from the 20th century.