I think MMA also goes through cycles.
We saw wrestling dominate with the likes of Coleman, Hughes etc.
Then it transitioned into standup fighters like Chuck, Arlovski, Franklin ('ish).
Then the more well rounded guys came through GSP, Silva, BJ
Now the wrestlers are beginning to show their heads Brock, Sonnen, Fitch etc.
It's not an exact science by any means but I do think there are some characteristics you can identify and group people of an era into.