I understand why some find Lyn to be a bit boring and bland, but I never found her that way. I really like her character, but that's just me. And as a unit, she's always been good for me. Her defense is never a problem because of how much she dodges, and even then giving her stat boosters helps out with that defense, same goes for strength. Constant critical hits is always nice, too. As for Eliwood, I just can't help but feel a little sorry for him, his dad goes missing and when he finally finds him he watches him die, then later on he kills the woman he loves Eliwood x Ninian is totally canon on accident, granted she comes back at the end but still. And then Hector is just a beast, pure and simple, almost impossible to hate such a beastly lord.
If I had to rate each lord from favorite to least favorite (not counting the ones from Japan-only games since I haven't played those), it'd probably go:
Lyn>Ephraim>Eliwood>Hector>Marth>Eirika>Ike>Micaiah>Chrom>Lucina