Great topic! My choices:

Apocalypse Now- 1979 Theatrical

One of my all-time favorite movies. I feel that Redux really messed with the pacing without adding anything substantial thematically that's not already there. A good watch for a fan, but I've argued many times that the first time you see AN, it has to be the theatrical.

Alien- Theatrical

Aliens- Special Edition

I wish there was a true "director's cut" of Alien 3. I think there's an above-average movie hiding somewhere in between the theatrical and assembly cut. Fan edits have gotten close, but fall short in various places.

Blade Runner- The Final Cut

A brilliant film refined to its utmost. I got to see the Final Cut in theaters, and it was amazing.

Terminator 2- Special Edition

Actually, I prefer ADigitalMan's fanedit that adds in the T-1000 searching John's room.