I saw this movie just last night on AMC. There are two ways to look at this movie: Scripturally and story-wise.
Scripturally the movie is not that good. There is a lot of license with Scripture (not surprising considering how small the book of Ruth is). But the license isn't really congruent with revelation. For example, this movie makes Ruth out to be a high priestess of chemosh and married for about 1/2 second to a Jewish man just before he dies. Boaz is a bitter man who makes a Moabite man drink poisoned water. The roles of kinsmen-redeemer is not even close to accurately portrayed. These things were done to try to make the movie have additional action, but detracts from the very real story. Also, here Naomi does not change her name, Moab tries to track Ruth down and kill her, and so on and so forth.
From a story perspective, the story is your classic structure. Boy meets girl, girl is coy, boy gets into trouble, girl rescues, boy says sappy stuff, girl falls in love, boy dies, girl moves on, girl meets new man, girl marries new man. And the actors do a good job with this standard plot line. For a movie made 41 years ago, it's still enjoyable watching. The production is pretty good and the acting is good. The sets remind you of Ben-Hur. The pacing of the story is standard for a movie made at that time, kinda slow (for today's tastes).
Overall the movie is fun to watch as long as you can overlook the Scriptural errors.