Matt Hughes is a legend in his own time, but a win over Serra for the title would've just kept it warm for GSP. I also REALLY wonder how Hughes would've fared in a five round fight against Serra, for I'm not all too sure Serra wouldn't pull a sub if Hughes plied his lay and pray style and their eventual fight was pretty even, moreso than expected.
The moment the sport began to evolve and Hughes didn't, he got passed by and is just slowly but surely declining. He got ruined against Penn, lucked out against GSP at 50 and beat the shit out of a completely gassed Joe Riggs after Karo dropped out. Since then, his record has been spotty at best and only really shined against a guy of which, the sport has passed by more than Hughes, in Royce Gracie.
As of UFC 79, I don't think Matt Hughes was really even a top 5 WW. At the time you have Kos, Fitch, Diego, GSP, Alves and Karo who I think all really pose a challenge to Hughes.
MY MMA RANKINGS
HW Velasquez Cigano Werdum Cormier Bigfoot Barnett Mir Browne
LHW Jones Machida Evans Hendo Davis Goose Teixeira Shogun Mousasi Bader
MW ASilva Rockhold Belfort Weidman Jacare Okami Kennedy Consta Belcher Boetsch
WW GSP Hendricks Condit MacDonald Diaz Maia Fitch Kampmann Ellenberger Pyle
LW Bendo Alvarez Maynard Melendez Thomson J.Miller Diaz Pettis Chandler Grant dos Anjos
FW Aldo Mendes Curran Lamas Frankie Zombie
BW Cruz Barao Fernandes Faber Moraes