Overrated: Master Chief
Halo fans worship this guy, and not for good reason. Most of them talk him up as a Spartan soldier capable of all feats, when really, what is he? Chief barely talks in the games. Additionally, he adds no drama or depth to the game by not doing anything out of the ordinary. Fortunately, he's not even in the conversation of what makes Halo popular. He's simply another character that became well-known because they were associated with a successful game.
Underrated: Tails
Brave, confident, and witty Sonic paired with the buff, incoherent powerhouse Knuckles make for an iconic duo. Many people tend to forget what I think is the most interesting and unique character in the series: Tails. His demeanor is that of any loyal friend; willing to help you no matter what. He's a bit on the shy side, but when someone needs him, Tails is there for help. He can fly a plane, or he can fly with his tail, and he manages to be completely modest about it. I'd even go as far as to say I wouldn't like Sonic without this friendly fox.