Since its inception in September of 2007, Moonlight has been variously compared to a number of other vampire shows, e.g., Blood Ties (2007), Angel (1999-2004), Charmed (1998-2006), Buffy the Vampire Slayer (1997-2003), Kindred: the Embraced (1996), Forever Knight (1989-1996), even Dark Shadows (1966-1971), the comparison claiming that Moonlight is a rip-off of some other show and that it lacks originality. Yes, there are similarities. They all have vampires in them, and some of the vampires have consciences and/or angst over being vampires, some choose not to feed on humans, some work as cops or P.I.s, some wear black clothes, some fall in love with a human, and some have superhuman abilities.
But there are differences that set Moonlight apart from these other shows. In most episodes, the bad guys are humans, not demons or supernatural beings. There are no hellspots, visiting Gods, vampire clans, or alternate universes. Mick St John [Alex O'Loughlin] doesn't rely on magic or witches to aid him in his work. He is able to tolerate small amounts of sunlight, so not every scene with him needs to be shot at night. What Moonlight does have is a fairly young vampire (turned in 1952) who doesn't have well-honed superpowers and centuries of experience behind him. It has a cure for vampirism, albeit temporary at this point. It has leading actors who are not spinoffs from other shows. It has what many think is incredible chemistry among the cast members. It features a family of vampires that are not harmed by fire.
Originality isn't the only way to judge a show. Many people go to the theater to see the same play performed by different casts or to enjoy a different interpretation of the material. All of the shows mentioned above can be deemed rip-offs of shows that came before them. Nearly every one has similarities to other shows. And that is not necessarily a bad thing! If you only had to stick to one show, and that was the end of that, then it would be quite boring. It's nice to have new shows, even if they have similar themes, as they obviously have a different cast and different plots. Hopefully, you'll watch Moonlight and enjoy it!