Pages with all their movies on. It would be cool not to have to go onto IMDB to find an actors filmography, and which ones I've seen etc.
Also, top 10 actor list?

Remove from charts users that don't check a movie for more than a certain time, like 6 months or 1 year. This will prevent cheaters who register and check lots of movies just to get a high position on charts and then never check a movie again. The accounts are kept and people can still access them. They only drop out of the charts in case of inactivity.

Since I can see on the main webpage the films my friends checked, I would like to comment on these activities, so I can ask him his opinion about it, and so on. I'm lazy to send a private message about it.

In simple words - please add a calendar, in which a specific user or group might add festivals, movie related events and movies (especially the obscure ones) screened in his/her region or country. This might allow other users from the group to find out and prepare for the event, and possibly attend it. This calendar could also be global (visible by all users) with the possibillity to limit the range of events to certain area by the use of tags (country, region, city etc.). It would also be great to allow linking to the webpage describing the specified event.

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/...

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.