Add how many people owns the movie among the other stuff like "checked", "favorited", "disliked" etc.

create a button who allows you to share the movie you watched with your friends in the social networks, such as facebook

Allow multiply users to edit a list. In addition to the current one-editor-per-list system, list creators could choose to make editing open to anyone, or have restricted editing privileges, where the creator has to approve new editors (similar to how groups work on the site).

Filter one's unchecked movies in favorited movies of another user. This will allow us to check the movies which most likely one likes from the nighbor's movie. This way one need not wait only for recommendations.

Similar tabs to the official ones could be introduced. Certainly I would like it very much if it would be possible to organize my favorited lists in categories like director filmography/awards/country list/general all time best lists/...

I find I often don't watch films because they are not on official watch lists, important films that are on many great lists that have not been made official yet. I hate letting this control my viewing and have been trying to fight it, watching films that are not official and then find that I'm falling down the chart. I just think that a real lover of cinema should not be limited to so few films. So, MORE official lists!!! It is the lists that brought us to this site, not social features, even though they are nice also. :)

On an individual movie page, I think there should be an automatically generated listing of "similar" movies based on the most frequently overlapping movies; i.e. the movies that have been most frequently checked and/or favorited along with the movie on the page by a single user.

if the data is kept, it would be nice to show how you've moved up in rankings (or progressed in a list) over time in a line chart

After users add new movies from imdb, unfortunately the film artwork does not come along with it. While it's understandable that with so many movies it's difficult to make sure that "Winter Beast" gets its just due there are also new films that don't have cover art (like Bad Teacher). But in both cases it's just a bummer sometimes to look at your list of recently checked movies and see a few with no real 'identity' in the list, even though on imdb the art is readily available.

Make a new list for series or soap operas

This button returns a random unchecked movie which is listed on one of the official toplist.

OS specific apps are nice, but designing the website-layout in such a way that it displays better on mobile devices (tablets and phones) is perhaps a faster solution.

There is a sizable issue that I've noticed with newer foreign films that initially had their Romanized names imported in, but have since gotten a proper English name.

Example: http://www.icheckmovies.com/movies/sseo-ni/ vs. http://www.imdb.com/title/tt1937339/

The idea is basically to have a simple goal of how many movies you aim to check (similar to the reading goal on Goodreads). This could be on a yearly or monthly basis.

I think the idea should be as simple as possible, but you could make it more customizable, too. I'd say you should only include feature films, but you could allow yourself other types. Or you could make it "in <x official lists" or something similar.

In any case, it works well for books and would presumably be a relatively small feature to introduce.

Instead of "like" "Dislike" or leaving it blank, I wouldn't mind a system that allows me to rate a movie after I watched it. It would also be interesting to see what movie has the highest "star" and lowest "star" rating.

Many foreign films are known by more than one name in English. Example Bergman's 'Gycklarnas afton' has the aka 'The Naked Night' but it is widely known as 'Sawdust and Tinsel'.

Instead of using neighbours to generate favourites, figure out which lists I like and make recommendations based on those.

It would be great to be able to import your own personal rating for a film from IMDb. Moreover, if we could see what our friends gave certain films, that would be even better.

Allow users to make multiple private favorite lists when using the "favorite" option. A small drop down menu could give users the options to add movies to a specific list of their own.

Eg.: "Mark movie as favorite in list...
Favorite Films
Favorite Animation
Favorite 1930s"
etc.