The size of a movie file is really dependent upon how it has been encoded.
This not only relates to the file type but the bit method.
i.e. You could have an .avi file with a resolution of 1280x560 and it could well be 1.5GB in size.
However, that same .avi file may have different encoded video and audio parameters and with a lesser 720x304 but have a much greater file size of 2.67GB
This is only the beginning, you also have many different file types, be that .avi, .mkv, .mp4, 3gp, .divx, .dat etc. etc. Have a
look here for the dozens upon dozens available.
Basically if you want a better quality video and audio movie you either need lots of storage or a device that can handle highly encoded data.
.mkv is very good at crunching large Blue ray 1080p & 720p to a fraction of the original data file but the cost is a decent processor and software that can handle hardware encoding.
Personally I find the Prime with
BS Player handles .mkv files very well.