In fairness, a Lena solo game would also include a npc Ian who would probably be more of a squarely good guy, struggling with his ex-girlfriend cheating on him, and struggling with his artistic pursuits. He'd be a natural foil to Mike, where instead of being the corrupting influence, Lena could be a supportive influence.
I generally think that Lena is more popular though because players like to see her corrupted. Ian's story is very much about bettering himself, but there's no one really trying to bring him down or make him fall. Maybe Axel or Seymour will become that to him, but even then, it's based on their relationship to Lena. If Ian ends up as mediocre as he started, it's due to his own lack of commitment. The closest corruption I can think of is the Cindy path, but no one is really encouraging him to make those choices and Cindy even tries to distance herself from him.
Conversely, Lena actually has forces working against her to try and make her submit to her or influence her. Axel, Seymour, and even Ivy are all trying to push and pull Lena in various directions that many would consider to make her less good as a person. Even if the characters in Ian's story are more interesting, there's very little conflict or drama in that path, outside of the Cindy/Wade situation, the Minerva job situation or what Lena herself introduces to his story. I'm interested by the involvement of Gillian though, because that does seem like it might introduce more conflict and drama for Ian's side of the story.
