Like with so much else regarding NPCs, Bethesda went with quantity over quality this time.
You get about 30 different followers, but they aren't really any different from each other, except for their preferred skills. The Companions, in fact, are all basically identical characters.
Meanwhile, you get 60 different marriage candidates, and they all literally have the exact same lines of dialogue added onto them when married. There is no difference between one and another.
Im sure some of the followers you get even have the same voice too

And marriage, ugh. I don't understand why they didn't just let you marry anyone if the whole marriage thing is so generic!
Wish you could marry a certain Dark Elf from the thieves guild, grown quite attached to her through our adventure of vengeance

Marcurio does have better dialog than most but I found him so ridiculously over powered that I've parted ways with him. Whilst I agree, as a general rule, companions are a major disappointment, I think dialog as a whole in Skyrim is a disappointment. Bethesda could learn a thing or two from The Witcher 2 where there was a brilliant moment once where I was just running along and a random NPC says "keep running around all the time and you'll give yourself a heart attack!". Just little things like that put a smile on your face but seem beyond Bethesda's ability to do because disappointing dialog is a reoccurring theme in TES games.
Haha, i have noticed he does seem to be blasting alot of my enemies to dust before i get a chance to even scraqe them with my sword. But at the moment im just happy to have a follower with a (very) small amount of character.
I'm not too critical of the dialog in general though, so far i think it's been quite good. Though i have been spending more time in the wilderness than in towns and around people though