Sure, android and ios and s60 then yes, but i wouldnt say that maemo is only a phone-os.
Most people who still stick to N900 does it because they need more than any phone-os can provide and since maemo is a desktop-os shoehorned into a phone, it is not only a phone but also can work as a replacement for a laptop, which no other modern phone os can do...
(Really old phone-oses like S80 and so, yes, but modern stuff, no )