I've seen (and own) both The Mummy and The Mummy Returns. I absolutely love The Mummy-the filmmakers managed to find that perfect balance of horror and humor. I can watch it over and over. The Mummy Returns, in my opinion, wasn't as good. It seems like they were trying hard to reach the same feeling of the first movie. But, I absolutely loved The Rock in The Mummy Returns. He is a wonderful entertainer, and should have a great career outside of wrestling.
I would recommend both movies, for those who like horror with a big dose of humor.