Dex:
A) Halloween. Greatest horror film ever made. Dare you argue?
...it's certainly up there but I wouldn't exactly call it a lock for first place. I think it's between Exorcist, Aliens, and Halloween, and I'm tempted to give the nod to Aliens. It's always been a personal favorite of mine, and it's full of memorable moments. Can you remember how you felt as they were standing in the room they'd sealed off, listening to the turrets firing, watching the xenomorphs get closer and closer on the motion sensor? Fucking thrilling movie.
B) Planet Terror is one of the two films in Grindhouse, it's the first one...didn't you just say you liked Grindhouse? Did you only see the second part, Death Proof?
I did, and I'll tell you why. I hate Robert Rodriguez. There, I said it. Now we all have to deal with it. I just fucking hate everything he's done. His part of Four Rooms sucked, the Mexico Trilogy sucked, and need I even mention The Adventures of Shark Boy and Lava Girl? The only things he's done that are even remotely worth a damn are From Dusk Till Dawn and Sin City, and honestly, I think even those are overrated.
Oh, and as for Romero? I hesitate to call that horror because it's so... unique. I'm more of the opinion that Romero created his own genre. It's heavily horror influenced, of course, but he mixes in that social commentary you mentioned along with some very smart humor and a kind of grotesque, over-the-top gore level that transcends anything in the horror genre in my opinion. The man, quite frankly, is a fucking genius in every way.