Have you ever thought of changing your rating system from 4 stars to 5 or 10 stars? I feel like you can't really compare so many different movies within a 4 star system. Like Horrible Bosses was way better than Bad Teacher and you gave them both 3 stars
I have mixed feelings about the star rating system. You are 100% correct that it creates seeming inconsistencies. On the other hand, it's the easiest to use. I didn't go with the five star system because it never made sense to me. A five star movie would have to be a classic, but you can't really assign classic status until the passage of time. Ten stars, meanwhile, seems overly complex. There doesn't seem to be much difference between, say, a 7 and an 8. So I've always stayed with the four star approach.
Then again, I always tell people not to focus too much on the stars. They are just intended to give a snapshot of my opinion. Hopefully (if I'm doing my job right) the text of the review will make it all clear.