I love the film, and I felt that having seen SG-1 even enhances the experience quite a bit. The original Stargate film is just so much greater in scale. The atmosphere, the sets, the cinematography, the music, it's all top notch, of course much better than anything from the show because of the budget. But then there's also the knowledge of the epic adventures that happen after the film in the TV show.
It's amazing how well the show ties into that film. Every element that is memorable from the show can be found in this film. And even Kurt Russell's Jack O'Neil has some moments where Richard Dean Anderson's O'Neill shines through. It's just that he's terribly depressed in the film.
I would have loved to see a sequel to the film that ignored the TV show and brought back Kurt Russell and James Spader.