Steffi. Their rivalry was unprecidented, but I have to say Steffi. My vote was closer than Bill over Kwame, Monica, had she not been stabbed, who knows what history she could have wraught on the WTA tour, but she has done enough, and will always be remebered as one of the greatest ever. But, she could never win Wimbledon, her movement wasn't that great. She had the mind for clay, and the shots for hardcourt, but she couldn't put together 7 consecutive wins at the All-England Club. That was one the main deciding factors in my vote. But yeah, I vote Steffi.
Career Grand Slam in your 20s? Been there done that. Career golden slam your 30s?
There's only 1. Serena.