Bilbo gave up the ring of his own free will - something even Frodo could not do, But, to be fair, Frodo's test was much harder (I take it the ring's power grew with proximity to Sauron) and so there can't really be any comparison. They are both similarly endearing and unexpectedly strong - Frodo, as Groin says, on a greater scale.
That said, the movies kind of ruined Frodo for me, sadly. That wide-eyed teenager was
not Frodo, and now my original Frodo seems to have vanished from my mind.
