monica/rachel joey/chandler are the strongest. but monica and joey had: tow the cooking class, monica helped with joeys.....wrap, joey was the one who talked monica out of getting a sperm donor back in the early days, joey helped monica hide her relationship with chandler, monica had a crush on joey (remember...she liked his arms
), joey married monica and chandler, and when they all thought chandler was cheating on monica with Nancy joeys comments "you son of a B!tch a crude comment but it shows how much joey cares for monica.
pheobe/chandler had some moments throughtout the series together but when monica says to chandler "we are not friends with pheobe anymore" chandler replies with "if she asks i protested a little..........but ok" but then he walks her down the aisle. so that one is a bit harder.
rachel and chandler: the one with all the cheesecakes, rachel set up chandler and joanna. chandlers goodbye to rachel was quick and simple but it wouldnt have matched chandlers character if there had of been more heart to it. he tells her he loves her and makes her laugh. and that is what chandler does after all.
ross/pheebs: pheebs takes ross to the airport to go after rachel in the last one, ross and pheebes made out on the pool table and probably would have gone further...but all the damn balls kept getting in the way (hehe love that ep), ross was pheobe's "backup", they lived together briefly.
damn, im sre ill think of more later!
but basically the show featured around the other relationships more as they were more important to the story line. 