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

Gav, u answered your own question in a few ways.lol

TAF and TZ were licenced movie themes, just like STNG and Indy Jones etc etc etc. Movie themes just outsold everything else, not withstanding Fishtales etc. As a whole, movie themes accross the majority of pinny companies outsold unlicenced non movie themes.

Same for Sega, Data East etc. Bally/Williams had junkyard and 4 or so other titles around that time which were all non movie themes etc, but their sales were low. One thing I will point out but, is all of them were based on movie themes anyway. TOTAN is based on Ali Barber and the 40 Thieves style of movies IMO, I think there was a movie called Tales of the Arabian Nights from memory, and even Scared Stiff features the Elvira lady who was on TV all the time, with Attack from Mars being based on 100 movies of the same theme/style Hollywood has made n remade 100 times over the years.  

Even themes like Medi Evil Madness are based on 100 movies like Robin Hood/Ritchard the Lionheart/Knights of the Round table etc, and the list goes on. Junkyard I would have to think about, but most unlicenced themes were all pulled from TV or movie shows anyway, but all got outsold by licenced movie themes.  

I would like to see someone do a unlicenced movie pinball. I dont care if its based on something from a movie or a TV show etc, something ballsy like Black Knight 2000 with 2 x seperate, and 2 x different level playfields would be excellent.