To be honest I rate films just based on how entertaining they are. That's really all, also whether or not they execute their concepts well. I am fine if a film doesn't bring anything new to the table, as long as it executes its concept and main idea astonishingly well. Hope this helps to fuel the movie discussion fire.

I've struggled with this for a while now. I used to judge movies based on other people's opinions. If I didn't like a movie that was agreed to be bad, then I was in the right. If I liked a movie that most people thought was bad, then it was a guilty pleasure of mine and I didn't talk about it very much. At some point I adopted a number scale that ranges from 0 to 3. Obviously you can probably come up with where good/bad films would fit within that scale. But 3 is a rating I would not give to very many films.

More recently I began thinking about critique philosophy a bit more. I decided that I would judge a movie on two levels: a personal subjective view, and a detached objective view.

I have since stopped thinking that way. Art is subjective and I have a hard time saying that a movie is bad if someone else liked it. Even if it is bad. Movies are made to entertain and if someone liked it, doesn't that mean it's good? I would say, only to them. If I think it's bad, then I think it's bad. I suppose I've worked myself into a loop of confusion. I guess I just judge a movie on how I like it, try to forget the objectivity, and keep my mouth shut about other people's opinions. Because we've all got differing taste in what we want movies to be.

Also, I've kind of dropped the number scale at this point. I want to remember a movie as either good or bad. A gray area wouldn't help in my opinion.

A typical 5-star rating system.

5 - Masterpiece, this is why we watch film.
4.5 - Excellent with a minor complaint.
4 - Very good, but a major element was missing.
3.5 - Good, glad I saw it, but nothing particularly standout.
3 - Relatively decent, the good outweighs the bad.
2.5 - Mediocrity, positives balance negatives.
2 - Below mediocrity, not worth watching.
1.5 - Disappointing, disheartening, heavily trite and boring to watch.
1 - If you look close enough in between the ***** you might be able to see a plot, extremely minimal positive elements.
0.5 - A waste of money and time on the part of the filmmakers and myself.

This rating system works best for me, but some mistakes will be made. I have The Room at 0.5/5 for its poor quality but I find it hilarious and quite enjoyable to watch, quote, etc as a result. I have stuff like Boogie Nights, Taxi Driver, etc at 5/5. I also collect film ratings here: http://letterboxd.com/TehCoolDawg/. A useful tool. I seem to be leaning towards 5-star reviews but that's because I go and rank all of my favorite films first, it should even out as time goes on.

Youtube | Flickr | Twitter

I was part of a group of four who rated movie critics.  The web site has been gone for a decade now, but we used every possible system.  We created a conversion chart.  The systems we used were:

1 to 10
0 to 10
5-star system, at 1/2 integer intervals
4-star system, at 1/2 integer intervals
Siskel & Ebert system (2 thumbs that can be up or down)
Some negative critic, which had a 5-point system where 0 was best and -4 was worst, at half-integer intervals
A few others I don't remember

The site had a weird layout.  At the page for the individual reviews, our avatars, all colored line drawings by me, appeared on the side.  You click each one for our personal review in a frame, and the ratings appeared at the bottom.

A few nights ago I was thinking about this and I came up with something I've kind of been subconsciously using. I'll rate a movie in 3 ways: Story, Technical and Entertainment. Like Star wars 7 (Which is the movie I was thinking about when I came up with this) Story: 7, Technical: 10, Entertainment: 10.
I read the posts above after I came up with this. They're very similar.