Janet Lynn would top my list. Part of the reason is that along with being so wonderful in herself, she was in many ways the forerunner of the modern era of ladies' skating, where powerful technique is married to true musical interpretation.
Laurence Owen looked to have been going in that direction from the small amount of footage we have of her, and it seems entirely possible that she would have succeeded Carol Heiss on the world stage as she did at U.S. Nationals. With her heritage as the daughter and student of one of America's greatest coaches (and former champions), Maribel Vinson Own, it seems likely that she would have been able to achieve a climb to the top.
Sasha Cohen I'd put on the list. Though Sasha had some weaknesses (in edging, certain jumps, and such), her strengths were so superior (position, constructive use of flexibility) that they put her above most other skaters of her time. By contrast, Lynn had incredible technique all the way around, including strong jumps and gorgeous edges and stroking. Her only failures seemed to be school figures and several unexplainable screw-ups that might have been due to nerves.
I think you all forgot Joannie Rochette.
And I'd add Surya Bonaly to pay respect to every precious character that enriched the world of figure skating.
But wait, Yukina and Surya have world titles .... as junior.
Janet Lynn by a landslide. She changed the sport. Not many other skaters can say that. They even put in the SP because of the uproar of the 1971 Worlds where Janet didn't even win a medal despite being the far superior free skater. The French people almost rioted they were so incensed that Janet wasn't on the podium. She even had to take bow because the people were calling her name.
I don't think Kostner and Cszisny should be listed since they are still competing, and theoretically Fumie too, though she will never win a spot on the Japanese ladies world team, barring injuries to their top 3 skaters.
I have only heard of Janet Lynn, and saw just one or two of her performances, so I am not going to list her, no disrespect meant.
From the skaters I have watched compete: Sasha Cohen, Caryn Kadavy, Surya Bonaly, Liz Manley, Yukari Nakano, Angela Nikodinov
I would not include Yukina Ota, though I loved her skating, because she never even competed at senior worlds.
I have to say Bonaly, she beat all the top competitors of her generation and won so many titles outside of Worlds and Olympics. Plus, of those who did not win she came the closest (missed '93 5 judges to 4, '94 5 to 4, and I think '95 5 to 4). Of course, she did not have good fundamentals and would have scored poorly under COP, but she was unique and I appreciate that she never tried to conform to what others expected her to.
Since I don't know that much about Janet Lynn, and haven't seen her skate, my vote goes for Sasha Cohen (although anyone everyone has listed is a viable candidate).