Characters in GTA4 sucked big time since you had to deal with them constantly. You would hate anyone if you had to take them out to bowling while playing this game on your leisure time. And Nico got the back draft of the suck from being such a bitch about it.
i'd say that has much less to do with the characters themselves and more with the game design. i would think replacing GTAIV characters with saint's row characters and putting you through the same dealings would only make matters worse -- much worse. saint's row characters aren't any better just because you don't go bowling with them.
Well, yeah. You are basically supporting my point there. GTA4 ruined what could have been potentially interesting characters if they didn't go into all the bullshit gameplay involving them. Volition knew not to go into that shit because it isn't fun to do.
Just go watch the Ronin Saints Row 2 trailer, it pretty much sums up why Saints Row has fun characters. They explain a plan to slowly and boringly infiltrate some place, but then you have Johnny '8 inch dick' Gat saying that they should forget the plan and go in guns blazing

In short: Saints Row characters = catalysts to provide player with enjoyment, fun, or entertainment. GTA4 characters = bog down gameplay with tedious never ending babysitting missions.