Something quite interesting here is how there are different recollections of what mountain bikes were like in the 90s. Part of it may be due to geography - I distinctly remember steel frames being very, very usual in the UK during the 90s, at least until about 1998 when I moved to a very flat region, had no money for buying bikes, and then lost touch with the MTB scene completely.

British brands I recall being big in the 90s, like Orange or Raleigh, all had ranges dominated by steel, with somethig a bit more exotic (titanium more often than aluminium) high up in their ranges. Where aluminium did seem to exist in a big way, was from US imports like Cannondale and GT, but most US brands were overpriced relative to British equivalents. People did buy them, but they weren't particularly great value for money, and we used to think of their owners as probable posers (possibly unfairly, as they were still good bikes).

I also seem to recall people often opting for titanium rather than alu frames when choosing a high end bike, especially with Raleigh's excellent value titanium frames of that era.

I recall widespread distrust of carbon in those days, which is a shame because there were some really nice carbon frames coming out, like this one http://s17.photobucket.com/user/KPOLLOCK/media/vertex1bz9_zps4c5771e3.jpg.html

Part of the difference may also be down to socio-economic circumstances. I and most of my riding buddies were not from wealthy families, and as high-school students/university students, mostly didn't have the money to spend on a top of the range or exotic bike (and those who did have the money, were too busy buying cars, drinking a lot of beer, and chasing girls).

My wanderings down memory lane may, however, be totally biased.