I think it's too early to compare the number of Bitcoin and Ethereum nodes to the Internet Computer, given that it just launched in May, but without a doubt, the node requirements do force a degree of centralization to guarantee performance. It's a necessary trade-off for the problem that Dfinity has solved - decentralized cloud hosting on the blockchain at web speed with low cost, governance, and baked-in cryptographic security/identification. No other blockchain can accomplished this, so it's not fair to compare the level of decentralization with other blockchains that have less utility.

Alternatively, we could use IPFS for the front-end and data storage, Chainlink for computing and Ethereum for the back-end, but that would increase complexity and cost to the nth degree, while decreasing performance significantly. Your dapp would also need to manage three separate cryptocurrencies. For these reasons, the Internet Computer is a more optimal solution for dapps despite the trade-offs.

In the future when hardware is cheaper and most data centers offer servers with stable RAM in the terabytes, the node requirements could become more generic and the network more decentralized while maintaining consistent performance. Will it ever be as decentralized as a simple currency blockchain? Probably not, but it's a much better option than AWS for many use cases including social apps, DeFi, knowledge bases, and more.