There's cheating, and then there's really cheating. All cliches aside, think about this, let me give this comparison:
In 1989 Lemond was clean. In that same year (Tour, Worlds, etc) Steven Rooks was on testosterone (by his own admission), so were a few other racers. It made little difference as to who won.
In 1991 Lemond was clean. In that same year it's speculated that at least a quarter of the peloton was on EPO. Greg exhausted himself, finishing 13 minutes out. In 1992 I'm speculating that 75% of the peloton was on EPO, some of them jacked up to a hematocrit of about 55. A clean Lemond lost 50 minutes on one mountain stage alone, his career over.
Riders in the past, form Merckx or Kelly taking ephedra based medicine, to Thevenet or Hinault taking cortisone shots, or even Rooks or probably Delgado steroid based testosterone, the playing field wasn't dramatically changed. You can't really look back and point our finger and say "if Merckx weren't on cough syrup, Edward Janssens wouldn't have finished an hour back and been ripped off." But it's pretty easy to look back to the early 1990's and say with certainty that Lemond, Mottet, Delion, Bassons and a few others were indeed ripped off.