A few records:

Highest winning % 10+ seasons:
1. Madden
2. Lombardy
3. George Allen
4. Ray Flaherty
5. George Halas
6. Don Shula

Most wins:
1. Don Shula
2. George Halas
3. Tom Landry
4. Curly Lambeau
5. Paul Brown
6. Marty Schottenheimer
7. Chuck Noll
8. Dan Reeves
9. Bill Belichick
10. Chuck Knox

Most years:
1. George Halas (40)
2. Don Shula (33)
2. Curley Lambeau (33)
4. Tom Landry (29)
5. Paul Brown (25)
6. Chuck Noll (23)

Taking all things into consideration, my top 10 coaches (in no particular order) would be:
1. Bill Walsh
2. George Halas
3. John Madden
4. Don Shula
5. Tom Landry
6. Chuck Noll
7. Paul Brown
8. Bill Belichick
9. Joe Gibbs
10. Vince Lombardi

I've removed Ewbank because he just wasn't very good consistently. I've taken Curly Lambeau off the list simply due to era. He didn't have to contend with so many things (play-offs, impatient ownership, free agency, a large number of teams, etc.). There are three 10-season coaches on the list (BW, Madden, and Lombardi).