I've only been paying attention since 2004, so I can't speak for Flomo, Trent, etc. Clearly, Washington is the best since I've been a fan. After that it would be Jerome Tillman, who was blessed with hops but not a lot of height, which hampered his dunking ability working in the post. Dunking on Osby of Maryland twice and the two huge alley oops against Akron are my fondest memories of Jerome.
www.youtube.com/watch
From there, I will lump Terren Harbut, Sonny Troutman, Johnnie Jackson, and Ivo Baltic in the same group. They all have had a few great dunks but not nearly as much volume as Devaughn and Jerome.