Beating Chuck in 2003 was a much better win than beating Chuck in 2007, Chuck was young and in his prime in 2003, that is a great win!
Based on what criteria?
In terms of...
...who's the best opponent he's beaten? Hendo.
...most important win in terms of furthering his career? Chuck II, no doubt.
...most brutal finish against top competition? Tie between Arona, and Wand III.
Best ranked win - Liddell both times
Most satisfying win - Wandy
Most entertaining win - Kevin Randleman/Ricardo Arona
Most underrated win - Dan Henderson
If you don't think it was Chuck 2 it's because you weren't around for it.
Hendo.
Arona was my favorite though
Best ranked win - Liddell both times
Most satisfying win - Wandy
Most entertaining win - Kevin Randleman/Ricardo Arona
Most underrated win - Dan Henderson