I think Shawn Fonteno did a great job voice acting him, but I'm question if he was needed for the story at all. I, like everyone else, was excited to "return to the hood" and re-live some San Andreas memories, as well as see crime from three perspectives, but it didn't work out quite well.
While Michael and Trevor have deep ties with each other, Franklin's relation to the other two is shallowed and feels forced. Also, he doesn't seem to have a lot of motivation to stick around with two middle-aged guys doing profit-less errand jobs for the FBI that could cost him his life while he already has a wealthy house in the hills.
He also complicates the ending, because it waters down the tension between Trevor and Franklin by making it less personal. He always felt like the odd one out of the three and just tagged along anyway.
For me, Franklin as a protag was dull, uninspiring and basically a sidekick for Mike and Trevor. You never really found out what made him tick the way you did with Niko. Or could appreciate/relate to CJ as he matured from a small time gang banging thug, into a major crime underworld power player--whose turf spanned 3 counties in SA.
I suppose I might have had a slightly different opinion if there had only been ONE protag (i.e. either follow the present day story of Micheal or Trevor based on the prologue we had in N. Yankton). The game would have technically been 3X as long and since Micheal's character is so shallow, would've made the game more fufilling. Then throw a curve ball and have Trevor show up and crash land in Micheal's life like he did in SP.
Being able to play 3 protags at will is a benchmark in GTA. But doing this resulted in the characters becoming superficial as SP lacked any meaningful depth due to the short storyline. So it might have been a lot better if R* made the game less painfully restrictive in it's sandbox mode style of play.
aka added lots of interactive interiors like MORE HEIST MISSIONS, ability to create sandbox style heists after beating SP, freight train/trucking missions, stealth/home invasion missions, working restaurants, fast food joints in drive up SR2 style, more interactive NPCs like drug dealers in the hood, working fruit stalls along the freeways, adding all of GTA IV clothing stores (since these store fronts exist in SP already), interactive boats where your char can enter an interior, buying multiple properties and business, boating/driving schools, casinos, dance halls, and yes---dating mini game etc etc. For a 5th gen game, GTA V still has exactly ZERO nightlife to date. SA was faaaar more lively and interactive.
If they couldn't do this because of time and/or budget constraints, then they should've at least allowed all 3 protags access to ALL the side activities each protag can currently do. It doesn't make sense how R* designed this system TBH.
Because it's plain stupid that Micheal (the expert sharp shooter of all 3 protags) can't go hunting??? Or Franklin (who can only own Smoke on the Water and has the hood/drug background) can't do Trevor's air/ground drug missions? Or can't play tennis? Or raid that weed farm up in Blaine county? Or why the other 2 protags can't deliver ped hitch hikers to the Cannibal Cult camp? Or wear women's clothing simply because R* decided to restrict this freedom to only one protag etc etc.
And no, that's NOT Franklin's house in the hills. It belongs to Lester who let him live there. Remember?