Honestly, I don't really think most of the relationships in the CE era were that great at all simply due to lack of any real meaningful/real development. The only one that showed promise like that was Athrun and Cagalli by the end of SEED, and look at how THAT wound up in SEED Destiny...
Relationships in SEED/SEED Destiny come off more like the people behind it just put characters together they felt LOOKED good together.
Otherwise, I never really truly felt that most of the pairings "loved" each other in a romantic sense.