Either Niko Bellic from GTA IV or John Marston from Red Dead Redemption.
I'm a real sucker for a good free roam sand box type game and Rockstar is also my favorite video game developer. Its hard to say cause I like the tough as nails attitude Nico Bellic gave off in GTA and not afraid of really anything and he probably isn't going to be in the next Grand Theft Auto since every game they use a new character. But John Marston has a more friendly attitude. Like in Grand Theft Auto he does most his task for money or to help his cousin as in Red Dead Redemption even though most of his task are cause of the government but there are some missions where he helps them just cause he is a friendly guy. And at first it seemed like he was going to be in Red Dead Redemption 2 if they ever made one but seeing as how the ending went he wont. But to see Jack Marston that would be great.
It would Probably be Nico Bellic since most video games already have a nice guy. Its nice to play a video game about a tough punk ass against the law.