There are only three imo, and that's the original trilogy. I've beaten the first countless times and just beat the second. I haven't started the third yet. But out of the first two, I enjoyed the first one more. It's more timeless. Never seems to get old. The second one (and I can only assume the third will fall into this as well) was great, but it felt like they were trying to do a little too much... which is rare, because I typically find sequels to great games to be the best ones.
We'll see how I feel about the third game. But it's going to be hard for it to overtake the first for me.