Religion: A set of beliefs concerning the cause, nature, and purpose of the universe, especially when considered as the creation of a superhuman agency or agencies, usually involving devotional and ritual observances, and often containing a moral code governing the conduct of human affairs.
Or: The belief in and worship of a superhuman controlling power, especially a personal God or Gods.
So, by these definitions found online, the JWs are a religion. They believe in a superhuman (notice, not necessarily righteous) controlling power, and they certainly are into maintaining a "moral code governing the conduct of human affairs."
Speaking for myself, I know that growing up I didn't think "our" religion was exciting. It was missing so much that other religions had: contemplative practices, beautiful churches or synagogues where impressive observances could be seen, wonderful holidays and worship days, schools and summer camps. Culture, art, and rich history could be seen, in my case, from afar.
Being a JW was like being in a bargain-basement religion, totally on the cheap. I was sad about this.