Samwise is definitely not underrated. I don't know how people 'rate' the different LOTR characters but I'd think most people would like him the most. He is always portrayed as the best, most pure character in the Fellowship, and arguably the best character in the movies. Frodo always sees him in a good light, and he's also the one who saves Frodo. All in all, I think most people rate Samwise 8/8.