I understand your point, but of course it is based on your definition of what the "Greatest Cowboy" is. Deion was a great player with great talent. There is no question of that. But others might have another definition that considers things like longevity with the team, whether a player is identified exclusively as a Cowboy or whether he is also strongly tied to other teams, whether a player was the face of the team etc ….
With Deion it's easy to get wide eyed over the pure athleticism and coverage skills, and of. course coverage is the most important skill for a CB, and he was probably the best ever at that. But I think it's reasonable to consider he was not strong helping against the run, and in fact it wasn't uncommon to see him shy away from tackles and just try to slow a player down without having to make hard contact.
As for his time as a Cowboy, that was only 5 out of 14 years - 36% of his career. He spent just as long with the Falcons, and had years with other teams. And only 14 of his 53 career INTs (26%) came as a Cowboy, and all his other statistical credentials were built more on his time with other teams than with Dallas. Like CouchCoach said in an earlier post, he was a mercenary who jumped from team to team.
