Is Predator the rare serialized franchise?

Not counting the AvP films, aren't all five Predator movies stand-alone? It's been a while since I've seen the first two but i don't remember the second one relating all that much to the first and the last 3 are all kinda their own thing, right?

I ask mostly cause I think the wife would enjoy Predators but might not really care for the first 2 so i wanna make sure there's nothing about those you NEED to see in order to appreciate Predators

Also are there other franchises where the movies aren't related to each other at all? Leprechaun comes to mind but that's it