The same could be said about anderson silva then.
Strictly comparing competition in the UFC:
Anderson Silva
Chris Leben - Unranked - KO
Rich Franklin - UFC MW Champion (Top 5 MW Then) - KO
Travis Lutter - Unranked - Submission (Elbows)
Nate Marquardt - 1st Title Defense (Top 5 MW Then and Now) - TKO
Rich Franklin II - 2nd Title Defense (Top 5 MW Then) - TKO
Dan Henderson - PRIDE MW Champion (Top 5 MW then and Now) 3rd Title Defense + Unified the UFC and PRIDE MW Titles - Submission (Rear Naked Choke)
James Irvin - LHW - KO
Patrick Cote - Unranked I believe - TKO (Injury)
Thales Leites - Top 10 MW (Then and Now) - Decision (Unanimous)
Lyoto Machida
Sam Hoger - Unranked - Decision (Unanimous)
David Heath - Unranked - Decision (Unanimous)
Kazuhiro Nakamura - Unranked - Decision (Unanimous)
Rameau Thierry Sokoudjou - Top 10 LHW (Then) - Submission (Arm Triangle)
Tito Ortiz - Unranked - Decision (Unanimous)
Thiago Silva - Top 10 LHW (Then and Now) - KO
Rashad Evans - UFC LHW Champion (#1 Ranked LHW) - KO
Anderson gets so much praise because he cleared out the UFC MW division and in the process, finished 4 Top 5 MWs (Franklin Twice, Marquardt and Henderson) Unified the PRIDE and UFC MW Titles, Has the most consecutive wins in the UFC (9) and holds the record for most consecutive Title Defenses in the UFC (6).
Machida hasn't come close to doing any of that.. YET. Like I said.. he has a wide open road ahead. Unlike Fedor, A.Silva and B.J. Penn, Machida and GSP are in divisions that have almost ALL the Top 10 fighters IN the UFC. So it's possible for a UFC WW/LHW to clear out 99% of the Top 10 (general consensus).
If Machida managed to do that, or even GSP.. there would be no question they were (at that time) the best because that's never been done before. No fighter (Yeah NASEDO not even Fedor) has ever beaten that many current Top 10 fighters in their division.