What titles are you talking about Cavey as GTB had very poor sales throughout the 90's and can be written off.
Williams were kings and the biggest seller they had in the 90's was High Speed with 17080 - GREAT sales for a non licenced game... Fish Tales outsold IJ by nearly 1000

Biggest sellers by far of the 90's were TAF and TZ... both unique games when they came out and both sales are yet to be repeated as has the impact these games had when released