Yes, Jimmy traded Walker for so much value...a brilliant maneuver nobody else would have thought to do, including Landry, obviously.
Yes, Landry started with garbage, and took the team to a championship, after 11 seasons, with fewer teams to compete against. Jimmy started with a garbage team and won a SB in 5 years.
Jimmy is most certainly synonymous with the Cowboys. Ask anyone you know who football's Jimmy Johnson is, and I bet 95% would reply that he was the head coach of the Dallas Cowboys. Yes, if asked the same question about Landry, 100% would give the same answer, but the RoH isn't about comparing them.
I don't know what the point of your last sentence is.
I loved Landry, and respect him still, much more than I do Jimmy, but that doesn't mean Jimmy doesn't deserve to be honored as well.