All were good at certain things and had a quality about them that drawer in the fan base that they have today.
But I feel like Todd and Grayson got their true " this is one of my favorites" fans from the other identities. Grayson(night wing) Todd(red hood) I don't see Damian as one of the best because of his rebellious behavior against his dad and he's just to much like batman just with a more killer instinct, he's a dominant character in the role of a sidekick. The rebirth teen titans help him out but overall he's a eh Robin.
That leaves Tim drake, not my favorite robin but skilled just like the others and his good quality was his intelligence. He was also a good well rounded robin and was one for a while, until his fans offed him of course so I'd go with Tim in terms of knowing his role and performing well in it without having to get some other alias to go by and truly being robin.