How about looking at performance in this years playoffs.
Rondo
18.3 pts, 11.9 asst, 2.8 TO, 9.6 reb, 2.7 stl, 42% FG
[Top Defender]
Paul
16.6 pts, 10.4 asst, 4.8 TO, 4.4 reb, 1.6 stl, 41.1% FG
[Top Defender]
Williams
20.2 pts, 10.8 asst, 4.2 TO, 3.8 reb, 1.8 stl, 41.4% FG
[Mediocre Defender]
Billups
19.6 pts, 7.3 asst, 1.7 TO, 3.7 reb, 1.6 stl, 45.0% FG
[Good Defender]
Parker
28.6 pts, 6.8 asst, 4.2 TO, 4.2 reb, 1.2 stl, 54.6% FG
[Weak defender, poor asst to TO ratio]
Playing head to head during the regular season, the ONLY point guard Rondo hasn't made look silly is Chris Paul.
When Rondo "older" PG like Nash, Kidd, Billups etc, he made them look like "has beens".
Also keep in mind Chris Paul was first team and Rondo on the 2nd team for NBA all-defensive teams this season. [I think Rondo should have been #1, but Paul won mostly due to reputation, not performance.]