The best replacement for french doors is sliding doors.

The best alternatives to french doors are rated as following:
★★★★★  sliding doors
★★★★  sliding glass doors
★★★  sliders
★★  slider
★★  sliding door
★★  patio doors
★★  atrium doors
★★  double doors
★  sliding patio doors
★  sliding glass door
★  side by side
★  sliding
★  sliding glass
★  side by side refrigerator
★  garden doors
  bifold
  french windows
  french doors
  bi fold

Your alternative for french doors is not listed? Suggest!
Speaking about french doors, one probably shouldn't forget about screens.

Other search terms related to french doors and their ratings are:
★★★★★ screens
★★★★ sidelights
You have in mind a companion for french doors and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of french doors in all years. Click on graph for more.
french doors
sliding doors
sliding glass doors