I don't think "The Cell" is the greatest movie ever made, or even close, but it's a fun romp, and I love flicks that question reality in some way. See also: Dark City, Thirteenth Floor
Heck, even Jennifer Lopez managed to act well in the movie, so that gets a few bonus points.
Beautiful set and costumes designs, too. If you haven't seen it, do so, highly reccomended by me.