The best replacement for forza 5 is gt6.

The best alternatives to forza 5 are rated as following:
★★★★★  gt6
★★★★★  need for speed rivals
★★★★★  need for speed
★★★★  forza 4
★★  driveclub
★★  forza horizon
★★  battlefield 4
★★  nfs rivals
★★  ryse
★★  nba 2k14
★★  project cars
★  assetto corsa
★  dead rising 3
★  iracing
★  gran turismo 6
★  gt6 graphics
★  fifa 14
  need for speed rivals graphics
  forza 5 limited edition
  gt6 physics

Your alternative for forza 5 is not listed? Suggest!
Speaking about forza 5, one probably shouldn't forget about xbox one.

Other search terms related to forza 5 and their ratings are:
★★★★★ xbox one
★ smartglass
You have in mind a companion for forza 5 and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of forza 5 in all years. Click on graph for more.
forza 5
gt6
need for speed rivals