You're looking at the wrong charts. Take a note of some Triple J Hottest 100 charts from the same years, and do some searches on youtube. I think you will be impressed on what you may find. A band that i still love to this day, Motor Ace, were an amazing Aussie band whose career was cut short due to illness.I absolutely love the 90's, soo much nostalgia for me. I missed out on the Grunge movement (Nevermind came out about two months before I was born) so I've caught up on that stuff about 10 years after it happened but love the stuff from the late 90's. Most of the stuff I heard off the radio or from movies like American Pie, Can't Hardly Wait, 10 Things I Hate About You and other teen movies that were out at the time.
Looking back at the charts from 98 and 99 there is so much stuff there that is soo bad that it's good for instance acts like Aqua, Smash Mouth, Vengaboys, Steps, B*Witched, Five, Sugar Ray but I still love listening to them even though my musical tastes have branched out to stuff like Classic Rock, Metal, Nu-Metal, Hip-Hop etc.