This choice might be a little controversial, which I would argue is the power of big, splashy memories. But the best #41 to wear the uniform was definitely Eugene Robinson, even so.
Robinson, of course, is best remembered for his brush with the law following an arrest for soliciting a prostitute, which came after he had been named the NFL's Man of the Year. He then had a pretty forgettable game against the Broncos in the Super Bowl, one that included him getting toasted a couple of times. That rough, miserable capper to his first season in Atlanta is his enduring legacy, but Robinson actually enjoyed a successful two year run for the Falcons.
That 1998 season saw him deliver four picks and solid coverage in the regular season, with a 77 yard interception return in the playoffs, as well. He was back in 1999, picking up another three picks and forcing a fumble. He was out of Atlanta the next year.
For his career, Robinson had 57 interceptions, 22 forced fumbles and 7.5 sacks in 16 NFL seasons played. That's a lengthy, terrific career for a defensive back, and it tells you more about Robinson's career than an arrest and a couple of lousy plays in the Super Bowl ever could.
Your next best choice is Tim Gordon, a free safety who started parts of four years in Atlanta, accumulating eight interceptions and serving as a very capable player for the Falcons over that span. This number is, admittedly, a little weak overall.