I believe that ETH will reclaim it's glory back once gas fee issue is solved, there is also a big difference between BSC and ETH that will still make many prefers ETH, that's the fact that BSC is Centralized and ETH isn't.
You must change the title, "Give reasons why BSC/BNB is better than eth" I hope that is a proper preposition and question you ask.
Well, I will give the reason why BSC is better than Eth,
1. Low gas fee
2. Much Faster than ETH
3. Much cheaper than ETH
4. More projects coming to BSC networks
5. Good and quality NFT games are also using BSC network. ( My Defi Pet, Cryptoblade, My neighbor Alice and many more, this all games chose BSC because they know that people nowadays are looking for better service specially a low transaction fee.