A list of the greatest sci-fi movie masterpieces has been compiled, with some outlets focusing on specific time periods, such as the last 15 years or the 21st century. The time frame considered varies across outlets, with some looking at the last 50 or 100 years, while others do not specify a particular period. The number of films included in these lists also differs, ranging from 6 to 50, and some outlets highlight specific films as particularly notable or genre-bending.