I run a one person game pretty regularly. The game is one of my longest running ever going for about 3 years now.
It started out as an Xavier Academy story. but as time has gone on, the character went on as a street level solo hero, to becoming an Avenger, and now leads her own Avengers team.
On the downside i'm swamped with running NPC's [currently I don't let there be more than 5 additional members to her team because I'd go crazy otherwise]. Starting out, the character was a student, and had NPC leaders for a while, til the player became more comfortable taking charge. At first, i'd have to have NPC's come up with a lot of the revelations, as the player wasn't used to taking initiative, but as time went on, i slowly began removing crutches one after another, until the char was able to form her own team and take charge.
Currently she runs a West Coast Avengers team in a world where only certain states rattified the Superhuman Registration Act. New York went Pro Reg, but California went Anti. She decided to give up fighting a losing battle against the Reg in New York, and started her own Avengers team on the West Coast. My current Storyline is Nimrod having infiltrated the government and attempting to make the Initiative seem incompetant, and getting Congress to adopt Project: Wideawake instead with the aim of wiping out Superhumans.