Sanchez was a big old moonballer who probably would have won only 1 slam without the Seles stabbing. Sabatini and Novotna are mentally fragile 1 slam wonders who lacked firepower or big weapons in their game. How on earth are they close to on pare with Venus, Henin, Clijsters, Sharapova, Davenport, and Capriati in caliber of play. Sanchez is comparable to those except Venus and Henin in achievements, but definitely not level of tennis.
Grafs only real competition was Seles and Navratilova, and Seles was missing for 2.5 years due to the stabbing, and Navratilova was only in her prime for about 3 years of Grafs long reign. I do agree those you mentioned were tougher competition and gave the Graf era alot more depth than the Navratilova era though. Navratilova had even poorer competition than Graf.