Only because Dallas did a lot with the picks. Johnson was a wheeler dealer, and used the picks to help him draft Emmitt Smith, Russell Maryland, Kevin Smith and Darrin Woodson. I mean, there were other pieces, but these were the impact players. The rest only lasted a year or two in Dallas.
Trading Walker just for Emmitt Smith would have been a steal for Dallas (as it turned out). but Maryland, Woodson and Kevin Smith too? Wow.
But as I said, it's only because Dallas got all those impact players. If they had drafted a bunch of guys who didn't do much, then it wouldn't be remembered quite this way.
A modern day example of a one-sided trade is the Jag sending Jalen Ramsay to the Rams for two firsts and a second. But nobody will remember this because the Jags will do nothing with the picks and continue to suck. Well, they will probably get one decent guy, so it won't turn out to be one sided in favor of the Rams.
But here is a VERY one sided trade that didn't start out that way. The jags traded with the Patriots to get a third round pick, and gave up a 7th that year and a 2nd the next year. The Jags got a decent CB named Derrick Cox with the 3rd round pick, and the Patriots got Julian Adelman and Gronk with their two picks. Think about that.