What really made the movie good was how many real rats they used in it. On the website it says they trained over 500 rats for this movie. It says Ben was played by an African Gambian rat, which is supposed to be the largest in the world growing from 4 to 7 pounds (regular rats get up to a pound). IIRC, the dog was a Pomeranian, which are really small dogs, so it very well could have been bigger. They also made it look even bigger with their little tricks in how they filmed it.
The original movie had a sequal called Ben, which I haven't been able to find yet. I believe the song "Ben" was originally written by Michael Jackson for the sequal. Its probably lame, but I love dumb movies anyway.
The new version is actually a good movie, but it didn't do very well at the box office. I think that was mostly because they didn't show it hardly at all in theatres. I actually tried to see it in the theatre and couldn't find anywhere it was playing.