The sad thing about today's Mainstream music is that what's current right now, will be old-fashion the following year. Rarely have we seen a Mainstream band still have Mainstream success over 5 years.
1991-1994 Was grunge, gansta rap.
94-97: Post grunge, 2 Pac, Biggie, Bad hip-hop, top 40 light rock, Punk
97-98: Techno, boy bands.
98-2001: Teeny Bop, Nu-metal, pop-punk, boy bands, bling-bling rap.
2002-2004: Emo, Garage Rock, Bling Rap, Bad Solo artists, and the "retro style.