I'm not sure why a spreading of the wealth in 1998 makes it weaker than other years, such as 2002.
In 1998, the Australian Open winner was #7 Petr Korda. In 2002, it was #18 Thomas Johansson.
In 1998, the French Open winner was #12 Carlos Moya. In 2002, it was #22 Albert Costa.
In 1998, the Wimbledon winner was #1 Pete Sampras. In 2002, it was #1 Lleyton Hewitt in 2002.
In 1998, the U.S. Open winner was #3 Pat Rafter. In 2002, the U.S. Open winner was #17 Sampras.
Korda was much better than ToJo, Moya was much better than Costa, and Sampras was much better than Hewitt. And while Sampras was much better than Rafter, 1998 Rafter was easily better than 2002 Sampras (heck, he even beat 1998 Sampras in the U.S. Open SF). 2002 seems significantly weaker to me than 1998. Jiri Novak got as high as #5 in 2002 and finished the year at #7 despite never making it past the 4th round of any Major aside from the 2002 Australian Open, beating no one ranked above #43 to get there.