There was always someone on a tear to challenge GSP back then, even 2 or 3 guys with winning streaks, highlight KO... I hate to see people bash on GSP's past opponents, because they did nothing great after GSP, but when those fight happened they were all top 3 fighters at their peaks. GSP just broke them
On his second run he had
Jon Fitch who was winning all the time and went for another 5 wins after being utterly dominated by GSP
BJ Penn was small but a P4P great at the time
Thiago Alves had 5 TKOs just before their fight and had won agianst Koscheck who was a top fighter
Dan Hardy was a UFC poster boy for the Brits but he was still on a 7 win streak with 5 finishes
Josh Koscheck was a big name, with notable wins, maybe the only one with Diaz that talked is way to a GSP match
Jake Shields was known as a winning machine he was on a 15 win streak, the MW Strikeforce champ he won to Dan Henderson...
Condit was interim champ and as legit as they come
Diaz kind of talked is way to go ahead of Hendricks, but he was still a legend with a 11 win streak before the condit running match
Hendricks was having wins and highlight KOs all the time for 5 years he was 15-1 when he fought GSP
After GSP it was still very good with Hendricks, Lawler, Wonder Boy, Rory, Woodley and Condit
But now, that well is dry, nobody can put together some momentum
100%. Overall, I believe the skills in elite MMA have increased pretty dramatically, but there's no doubt that WW is looking pretty thin at this point. The current best guys:
Woodley- Champ, pretty comprehensive skillset with crazy athleticism and power.
Colby- A solid wrestler, but a small WW with no power or serious striking skills
RDA- an excellent overall skillset, but a very small WW, pretty decidedly past prime, and a documented weakness against wrestlers
Maia- extremely one-dimensional, well past prime
Usman- a similar fighter to woodley, but worse in almost every metric
Lawler- after 15 years, it looks like his chin has finally quit
Wonderboy- very closely matched with Woodley, but at 2 stinkers, will almost certainly never get to fight him again
Till- well, we all saw what happened there...
Most the top ten right now are career journeymen (magny, masvidal), small (Colby, Rda), old (maia, RDA, lawler), inexperienced (Colby, Till), or already lost (WB, Till, Lawler, Maia). There's still a couple good matchups out there, but as a whole, WW is extremely shallow.