The Other Big Bands of 91 might have had more success,ie Warrant, which went in a harder direction in 92, Skid Row had a #1 with Slave to the Grind in 91 and the metal scene as a whole may go more thrash. If Axl can keep it together GNR may be even bigger w/o grunge. Metallica and Megadeth sound may become an even bigger force in metal. And more Rap-Metal Bands might emerge if Faith No More gets bigger.
Rap music might do much to fill the void, maybe getting more of the mainstream white audience as fans than in otl.
It could be either or. Rap and metal might split the white audience pretty evenly. Some bands that never broke big as a result of the pop metal scene like Testament might get really big as a result of no grunge scene. Megadeth's
Countdown to Extinction with tracks like "Foreclosure of a Dream" might become a statement of an era. Slayer would earn a lot of criticism from parents groups for being Nazis with the track "SS-3" from 1994's
Divine Intervention, resurrecting the debate that started with the song "Angel of Death" from the
Reign in Blood album. Testament would gain a huge audience with
The Ritual in 1992 and 1994's
Low. Queensrÿche would continue to push forward, becoming one of the biggest bands of the early 90's alongside Metallica and Megadeth despite being progressive metal and not thrash.
Of course, there's also room for more than just big bands of the thrash scene. Iced Earth would probably have a higher impact early on if enough underground press goes nuts about
Night of the Stormrider. Grave Digger would lead the charge with its comeback album
The Reaper as would Blind Guardian with
Somewhere Far Beyond. Savatage would probably continue to possess a wide audience as well, possibly butterflying out Trans-Siberian Orchestra in the future. Dio would probably enjoy a pretty decent return to a solo career after leaving Black Sabbath for a second time.
Rap would probably have the impact of the alternative to the metal scene and could be instrumental in overtaking it in popularity in the late 90's as thrash metal bands get older and power and progressive metal lose their appeal. Death and black metal would continue to play underground, now joined by a slew of thrash and power metal acts that couldn't make it big in the early to mid-90's.
So here is my list of guaranteed big metal bands in this scenario:
Metallica
Megadeth
Queensrÿche
Anthrax
Slayer
Testament
Dio
Ozzy Osbourne
Possibly:
Savatage
Grave Digger
Blind Guardian
Dream Theater
Manowar