You've gotta give it up for the debut, particularly when the debut is as strong as this one. The story of two members of Napoleon's army who spend years (long stretches of which are broken up by their participation in war) engaging in a series of duels. It's a great historical drama, not to mention a psychological character study.
Oh, but which version? I guess you'd have to go with "The Final Cut," but I'm sure every version has its champions. One thing that remains the same across all versions is the visionary look of the film which has continued to influence science fiction films to this day.
The film that introduced the world to Ellen Ripley has to be given its due. Plus, it's one of the greatest science fiction films, and one of the greatest horror films, ever made.
Scott isn't really someone I would characterize as a "feminist filmmaker" but his work on Thelma & Louise makes a decent case for it (even if it is a particularly violent, perhaps even militant, version of feminism). Politics aside, that the film continues to have a cultural impact, as demonstrated by the various 20th anniversary retrospectives that came out last year, proves its effectiveness as a film.
Without question, Scott's best film. An intense and thrilling film, it was also, unfortunately, somewhat underappreciated at the time of its release, securing 4 Oscar nominations (including a Best Director nod for Scott) but failing to make the Best Picture roster. Still, it's the standard by which Scott's films should be measured.