I think the 100 kph is confusing you. That's only 62 mph.
Average speed of 60kph= 37 mph. For roller coasters these days, that's not fast at all. The coaster at Six Flags goes 128 mph, over twice as fast and it gets there in only 3.3 seconds.
And as for the Top Thrill Dagster, Kingda Ka, the new one at Six Flags Great Adventure (Jackson, NJ) is taller and faster