I don't see a serious competitor for Ethereum now. Ethereum is still difficult to follow by other projects because most people already trust in Ethereum so much. Maybe someday Solana and Polygon will be serious competitors for Ethereum because those 2 projects have very potential future. However, Ethereum is still very far from those projects now. There is no sign of big competitors of Ethereum in the near future.
BNB, Solana, Polygon will be the best competitor for ethereum.
Ethereum is the biggest as smart contract platform.
but I think it will take a long time.
Polkadot not popular as ethereum and BNB , i don't think Polkadot will be there.
Compete to ethereum and BNB.
If their team will improve their project , I think polkadot has potentially to compete to ethereum and BNB.
Because we know ethereum is the second rank on CMC, BNB is number 4.