The comments about throwing the background out of focus are definitely on-the-money. I would also suggest that longer lenses tend to yield more "cinematic" results. (Which is not to say that wide / slightly-wide perspectives can't also be dramatic. But when shooting video with a wide lens, perspective distortion starts to get quite noticeable as you pan around.)
However, the lens is just part of getting a cinematic feel.
Just as important are using composition, lighting, and post-processing to heighten the dramatic feel. I'm going to do a Flickr search for "cinematic" and choose a few examples:
Features of note:
- Framing/composition within a "letterbox" aspect ratio.
- Tight control of the color pallete
- The scene is slightly flattened, which suggests that a long lens was used
- Heavy vignetting
- Muted palette
- Long lens
- Dramatic lighting
- Slightly-wide lens
- Look at that high-contrast lighting!
- Muted color palette
- Long lens (probably)
Also check out the Cinematic pool for more: http://www.flickr.com/groups/cinematicinfluences/pool/with/4112078800/