That depends on the scope and scope type. S&B 5-25x56 still acquits itself pretty well and is easily a top tier scope. The latest TT and ZCO design are, generally better, but it is the same class of scope.
With some other designs, like LPVOs that went through a significant development process in the last decade, there is nothing from 15 years ago that would be truly competitive with them.
In general, I think the most improvement overall was with $1500-$2000 scopes. A 15-20 year old $1500 scope can't hold a candle overall to the modern designs in this price range.
ILya