Before their fourth fight, I actually had Izzy Vazquez and Rafael Marquez as my #1 trilogy ever (at least of all the ones that were filmed). Unlike other famous trilogies, all 3 of their bouts were excellent fights and closely contested. However, the fourth fight was sad to watch. Good for them for getting bigger paydays for the hell they went through, but Izzy shouldn’t have been in the ring with those eyes issues. I read that they had a special protective gear for him in training to try to prevent cuts, and he barely even sparred. Because of that, and the way Manny Pacquiao-JM Marquez 4 ended, I lean towards ranking that series higher. Sugar Ray Robinson and Gene Fullmer had a memorable quadrilogy, featuring one of the greatest one-punch KOs in history in the second bout. Azumah Nelson and Jesse James Leila fought 4 times in the 90s. Bobby Chacon-Bazooka Limon 4 is one of a number of classic fights in late 1982. Similar to Vazquez-Márquez 3, it featured a final round knockdown in a fight decided by one point on the cards. I haven’t seen the others, so I don’t know where exactly to rank this series.
Wonjongkam Vs Naito was a pretty interesting one Blow out in the first fight Win for Pong in the second The third struggled to get TV, meaning most in Japan missed Naito's win The final being a draw Sahaprom Vs Nishioka was a good one too, very, very competitive over all Certainly not the most exciting on a bout by bout basis but two compelling 4 fights series all the same
Chacon-Limon Vazquez-Marquez Gonzalez-Oguma Marquez-Pacquiao Fullmer-Robinson and Nelson-Leija is a good mention. Griffith vs Rodriguez is bound to get mentioned, but I've always found it impenetrably boring.
Of ones where we have ALL the fights, Chacon-Limon, Robinson-Fullmer, and Griffith-Rodriguez. Walcott-Charles maybe, but the entire series is not great. IV is an absolute snoozer for 2/ 3 of the fight. I honestly cannot think of any others. Quadrilogies are rare, but usually yield great results.