I'd probably go with, 1. The Thing 2. The Fog 3. Halloween 4. Assault on Precinct 13 5. Big Trouble in Little China
You forgot Escape from New York. That's pretty much it, except that instead of seldom remembered Big Trouble in Little China I will pick "They Live" as his third most enduring classic.
1. The Thing 2. They Live 3. Halloween 4. Christine 5. The Fog I gotta confess: I never really liked Escape from NY or Assault on Precinct 13. Matter of fact, I find the Assault remake with Ethan Hawke and Lawrence Fishburne to be a better movie. Christine was on TV a few weeks ago, and I rewatched it. It's still an entertaining horror flick. The Thing, They Live, and Halloween are all classics.
One and two could flip flop depending on my mood... 1. The Thing 2. Halloween 3. Big Trouble In Little China 4. Escape From NY 5. They Live Honorable mentions: Christine, Assault on Precint 13, The Fog...