"All time" wil be used in this context : Best rated of "all time". Will be displayed clased to "Best rated of the month", "best rated of the week". You can also translate "Of all time" if you prefer.
this is kind of hard for doing in Hindi because there are different words for different usage. He says this all time. Here all time = हमेशा, best rated songs of all time = हर वकà¥à¤¤ के बेहतरीन गाने. etc