I agree with the OP: the iPhone 4 remains the best smartphone ever made. No competition. Or should I say: plenty of competition but no equal.
Many will argue with this point. Other phones check more boxes in some areas... Better notifications, faster processors, more RAM, etc. etc. But the end result that matters for 95% of people is the overall experience. How responsive is the OS? How reliably does it work? How easy is it to buy and install an app? Apple may exercise more control than other manufacturers, but they leverage that control to provide a highly polished user experience, and it shows.
Also I'll toss another item into the love-fest: the outrageously good retina display. Apple really went all-out on that screen, and 8 months later it is still truly amazing.