I enjoyed everything BUT Franklin's storyline. The real story is about Michael and Trevor: frankling is just used as a device to move forward the story, but it has almost no real personality...ok, he has SOME personality, but his relationship with his friends are so under-developed that, at the end of the game you know not too much about him. As Trevor said in one of the missions, "franklin makes us multicultural" and while I don't think he is totally fair, there is some thruth: franklin at times looks just like a "token character" that has been created just to please part of the consumers (expecially those who screams "there can't be Los santos without gang wars!!!"), but without much effort to make him three-dimensional and complex. And before you start to attack me cause "i'm a racist", think about gay tony:; he could have been just another "token homosexual character", but instead he was well written into the storyline bringing a new point of view in the story. This isn't the case with franklin, sadly.
Michael and Trevor are the two real stars of the game, and I LOVED their sections. They are far more complex characters that you can think, and the tension between them feels real at times. Sadly, there is no real resolution about their conflict in the storyline (just some random dialogue after the last mission, but I don't see them as "storyline"), and I think the last mission is where R* failed to deliver a strong ending.