My son plays Nintendo all day
My 4yr. old will literally play nintendo all day, everyday.
A guess would be that games make him feel powerful and competent. The world is not a friendly place for wee little kids. They want to do so much and rules and society and even their 4 yo bodies prevent them from doing what they want to do. But games they can do. They can beat the bad guy. Or get the car around the track faster than anyone. Or collect hundreds of gold coins.
Some kids have desires that are in keeping with what they can do physically and socially. Some kids don't. For instance some kids are perfectly fine accepting the pace at which they learn to ride a bike. Some kids want to be able to ride well before they have the mental and physical development to be able to do it. And it's frustrating to them.
He refuses to go anywhere or do anything else which is not alright with the rest of us who would like to do something else.
That's just going to be part of his reality. And maybe if you picture what he's doing as something you value -- like drawing or whatever -- you'll be able to draw up the understanding to help him transition to something else. Give him warning. Tell him in the morning what the plans are if you can. Help him get to a saving spot. Assure him he'll be able to get back to it when you get back home. (And make sure that happens so he knows you mean it and it's not just a ruse to get him to stop.) Do what you can to ensure the time he's away is pleasant and show him you appreciate that he's giving up his time. If my husband dragged me away from the last chapter of a book to do something tedious and my only reward for giving him my time and interrupting something wonderful was being returned home eventually, I'd resent it. Maybe express to your son in passing as you might to a friend, "Your brothers really are enjoying themselves doing that, aren't they? I'm really glad that I'm able to be with you guys all day so they can have fun like that." (But it will have to be an honest expression of your feelings, not a way of making him feel the "right" way. Kids are pretty good at picking up manipulation! ;-) And talk about appreciating his freedom to be able to do what he enjoys to the other kids too. That will help him with the skill of seeing the world through other's eyes. (Something that can take some people years and years to acquire!)
He gets cranky, occasionally pees or poops in his pants while playing because he doesn't want to be interupted and generally becomes so irritable that our whole family suffers.
I would separate the actions from the reactions. It's not the game playing that's a problem. If he were spending hours sculpting clay into fantastical creatures and couldn't stop to go to the bathroom, would that be a problem?
It's his ability to handle his emotions after hours of intensity that's a problem. It's his ability to interrupt something intensely interesting to do something boring and irritating that's a problem. It's his ability to transition to something else. It's his ability to set aside his own needs to allow others needs to be met that's a problem. Those are all skills that are useful for a lifetime that he can be helped with. Some of those skills he might be able to do now with some help at awareness. Some he might struggle with because he isn't developmentally ready. Just as some kids can speak fine except for certain letters. It will come with time and opportunity to learn.
(It was a joke, but on the game review show X-Play (on Tech TV -- it's a really funny show and we're not even big gamers! :-) they had some made up gaming inventions. One of them was The X-Play Gaming Pants -- adult diapers -- for extended playing power. ;-) So hard core adult gamers find interrupting for the bathroom an annoyance too and they've had 4 or 5 times the practice at living your son has.)
I should take a shower as soon as I get up in the morning. But I really want to get writing. And the light in the bathroom takes an interminable minute or two to turn on. But if I sit down at the computer while I wait for it I can be there for 2-3 hours. And then my daughter Kat wakes up and I'm faced with having to help her find something to do on her own at some point so I can take a shower.
I'm an adult and I should be able to do the "right" thing which is take a shower as soon as I get up. But I really really want to write and the bathroom light takes so very very long to come on that I usually end up on the computer and faced with the shower problem.
If people grumped at me -- well I should change because I'm an adult and shouldn't need people to grump at me in order to change -- but I would feel grumpy in return, the home would be full of negative energy and relationships would be battered.
What would work better is if someone were up before me and left the light on in the bathroom. Or if I asked my husband to remind me. (I wouldn't transfer the burden to him. I wouldn't expect him to make me take a shower or blame him if he forgot to remind me.) Or if I put a reminder note on the computer. Or lots of other things that respected that I will change when I am able to change.
It's helpful to realize that we can't make people change. People will only change when they choose to change. We can make the circumstances around them so unpleasant that they choose to change to stop the unpleasantness but in the process everything fills up with negativity and we tear at relationships. Or we can recognize that kids are doing the best they can at the moment and help them acquire new skills. We can be people that they want to help and want to change for, rather than controlling harridans they wish would go away.
If he were drawing for hours and turning out wonderful stuff that you wanted to encourage him to continue doing, it would probably be easier to see the solution.
Ask him periodically if he needs to go to the bathroom. When you're near him, be aware of his body language so you can see that he does need to go. Help him get to a saving spot on the game. When you can entice him away with something else, ask if he needs to go to the bathroom so he won't be interrupting something fun just for something boring.
When he's cranky, talk about that. Tell him in a calm matter of fact voice that you won't let people treat you like that -- if he's hitting or saying nasty things. Or tell him that you can't help him unless he can speak clearly and calmly. Or whatever will give him information and awareness about his emotions and how they affect others.
When he's in the midst of crankiness it's helpful to realize he doesn't feel wrong. He feels the whole world is wrong. Telling him he's the one that's off isn't going to change his perception. But giving him feedback that grumping at people won't get him what he wants very efficiently -- no matter how "wrong" the rest of the world is being at the moment ;-) -- will be one step in him gaining greater awareness of what's going on inside of him and what's causing it and how to handle emotions rather than just reacting to them.
The goal shouldn't be to stop what's causing the emotions. Life will always be throwing things at him that will cause his emotions to rile up. So the goal should be to help him deal with his emotions.
Some of the skills he needs is an awareness of his body so he notices the build up to crankiness. He can't take a break until he has the ability to notice when he needs a break. You can talk about what he feels when he's playing. It's possible he won't know but asking periodically will help him be more aware so when he's developmentally ready to notice, he'll have that awareness in place.
That will be a long process. Some adults haven't mastered what to do with emotions -- probably because they were told to shove them down and not display them.
Kids often feel slaves to their emotions. They get these feelings and they feel they need to react however they feel. Like hitting when they're angry. Or screaming when they're frustrated.
You can mention -- perhaps when he's not cranky -- that you've been noticing that he gets mean with the family after he's been playing games for a long time.