Dell stock from 1990 to now had an average return of ~30% per year. You could have lost money if you bought at the peak but it would have still been an awesome return over 20 years. So yes it's only worth ~200x you initial investment now vs. ~800x I don't think anyone who bought in 1990 really cares all that much. And it’s not just Dell Microsoft did the same thing as did several others.

PS: From 1990 to now the Nasdaq beat the Dow.

Yes, dell has awesome returns from 1990 to today. We were not in a bubble in 1990. If you bought into dell between jan 1999 - august 2000, you are still in the hole by at least 50%, and possibly by up to about 70%. If you bought it at the peak, you were very badly screwed.

If you bought it in 1990, the correct investment decision would have been to sell it in late 1999-mid 2000 when it seemed to plateau, and possibly buy back in to it later. However you look at it, staying long in a bubble is always irrational. Even if the company performed miraculously before the bubble and will perform miraculously after it, you can only lose by holding it in the bubble.

(Of course, this predicates knowing when the sector is in a bubble. Which, suffice to say, is hard.)

There are two definitions of a bubble you can look at the current value and say the point where the market started to over value the winners at which point dell, Microsoft, and Cisco where not in a bubble prior to 1997 and it only lasted around 2-4 years.

Or you can look at the bubble from the point where explosive growth started around 1998-1990 and died in 2000.

PS: Looking only at winners distorts the picture, so while MSFT was still undervalued (relative to its current dividend adjusted price) in 1996 there were also plenty of overvalued stocks in 1996 that tanked.