Salah is not anything close to being the best African player of all time. He's a fair entry in the discussion but not a genuine contender.
I would argue, he's only the second-best Egyptian player of all time. The best would be Mohammed Aboutrika in my opinion, based on his achievements at both national and club levels.
Aboutrika also would be a more logical candidate for best African player of all time, and for me, he is joined at the very top by Yaya Toure.
I would say, Salah, Mane, Eto, Mahrez, Drogba, Kanu, are all next-tier greats.
Weah I can't say much about because I never watched him play. He did win a Ballon'dor however.