If I have to recommend 10 movies to the users Let's say I have some information about a user and movie data similar to the following:

user: age, gender, height, nationality, etc
movie : actor, genre , director info
userwatch : userA watch movieA at 2009,,.......
userComment : userA comments about movie 


In this case, if I would like to recommend 10 movies to each user, which machine learning technique would I use?

I was thinking about making a data frame and running RandomForestClassifier, but in this case, it's hard to recommend exactly 10 movies to each user.

I was also thinking about using K-means clustering, but when the movie number is over 200000, i'm not sure k-means is the best choice.

Any help is greatly appreciated.
Use a recommender system.

I suggest you begin by reading an introduction to recommender systems.