It's an amazing concept and R* should definitely stick with it in future installments, but they didn't nail it in V. In perfect version of V, all three protagonists would get the same amount of focus. In released version of V, only Michael got the proper amount of focus, with Trevor and Franklin being glorified supporting characters.
You just can't make a GTA game that is just about as long as IV and then cram three protagonists in it. IV + Episodes worked, because Niko got the whole game for himself and then Johnny and Luis got each 10 hour side stories. Also, IV and Episodes really offered three completely different views on Liberty City and its underworld. All three stories in IV dealt with different themes, however V, in the end, even though there were three characters with completely different backgrounds, boiled down to high profile crime and FIB/IAA stuff. We never got as good look on Los Santos' street gangs and Blaine County's outlaws as we got on Alderney's biker gangs and LC nightclub scene in IV.
But, looking back, we should probably be happy V's story turned out as good as it was. In an attempt to make V's story more balanced, R* could have shafted Michael's story too, which would be a disaster, since we would end up with no good story at all. Like I said, a game must be significantly longer to support three protagonists.