What I mean by serious is, take out all the jokes, references, and stupid easter eggs, and give us an insane story line where we have sympathy for the character.
I have an idea for a more serious GTA.
You could start out as a 19 year old thug in LS, then, when your friend gets killed by a balla, you decide to join the Families for revenge. You would be part of the families now, and it starts out good. You're taking out your pain on the ballas. But after a while, you don't like the other crimes your gang partakes in. EX: murdering innocent people.
You want out, so you try to run off to San Fierro where your other childhood friend lives. He lets you live with him after you tell him that you betrayed your old gang. Your friend gets you a job boosting cars and street racing for some money.
but the families soon find out where you are, and you once again go into hiding, booking a motel in whetstone. While in your motel room, you get a phone call from a LSPD officer, and he tells you that he will help you get out of the mess that you are in, but he would need 500k, or you would need to do some jobs for him.
Once you do that for him, you find the worst ghettos in LS, and he gives you a fake ID so you can join the cops and help them sweep the area of the families. You find out that a friend from the families has survived, and he tells you that he would end everything if you do some jobs for him. (Fly to mexico, get drugs, and bring them back to LS). You have two choices, do it for him, or kill him and have to give away everything you earned (Custom cars, guns, money) to the cops as evidence.