Predator 2 was meh, maybe even a little boring, but I'd still put it above Predators. That movie was shit. Shit cast. Poorly executed story. (Interesting idea, but seeing it on screen was extremely anti-climactic). Plus, Predators felt like a massive super inferior ripoff of Predator. So many times I was like "this is just a rehash of what I've already seen and what was done much, much better before"
So I'll go with Predator 2.
In reality though, Predator never got a good follow up. Predator is a classic. The rest are varying degrees of shit.