It may seem like a strange strategy to segregate 10 year old children based on one or two personality traits, but this is how Hogwarts operated for hundreds of years. Every House was supposed to have their positive traits, and yet it came to be that many children looked down on Slytherin, and were scared of being given the green robes.
Instead, everyone wanted to be in the scarlet and gold of Gryffindor, and to be seen and judged as the bravest, and the best that there is in the wizarding world.
While there have been notable and successful wizards and witches from all four houses, it cannot be denied that most of Hogwarts' greatest success stories followed in the academic footsteps of Godric Gryffindor. They are the bravest, the most courageous, and the most determined, and usually the most famous outside of the wizards that turned evil.
Whether they have come from a long line of a Gryffindors, were brand new to the wizarding world when they arrived at Hogwarts' doors, or have since gone on to become professors at the very school where they first learned magic, there are some very powerful witches and wizards that came through Gryffindor.
10. Peter Pettigrew
All four houses at Hogwarts are supposed to be equal, however that clearly isn't the case in reality. All the greatest wizards came through Gryffindor, and according to Hagrid, there wasn't a wizard that went bad that wasn't in Slytherin. There are exceptions to these rules however, one of which is Peter Pettigrew.
Knowing what this particular character did, it's hard to see why he was put in Gryffindor at all. He betrayed the trust of Lily and James Potter, and he lived as a rat in Ron Weasley's pocket for years in hiding.
On the face of it, there doesn't appear to be a brave bone in Wormtail's body, though it could be argued that cutting off your own finger takes a certain strange kind of courage. His crowning glory however, and the act that made him one of Gryffindor's more brilliant students, is the fact that he became an animagus.
The transfiguration spell and action required to do such a deed couldn't have been done by just anyone. A single mandrake leaf must be kept in the wizard's mouth for an entire month without chewing, swallowing, or spitting it out. Between this leaf then being added to the potion and the next electrical storm, which could be years away, the wizard must recite the correct incantation every single night without fail. This is something that Peter Pettigrew would not have been able to achieve if he weren't a great wizard.