I agree with all the moms that have posted.
This is just a phase. This also might be a control issue because this is something that kids can control, especially if they are getting the food they want and when they want.
Close up any distractions (TV, radio) and make this a family dinner. Encourage him to tell his dad what he did today, build blocks, color, play a game, help with his sister by getting the diapers, whatever. Just really get him to interact with the family. Kids do not want to spend time at dinner if they can get down and go watch a TV program or play toys. His age is going to be bored greatly if he has to just sit for a period of time (it is like a time out to him), and he might just take a bite or two because he is sitting there.
Serve SMALL portions of everything. He might be overwhelmed at seeing so much food. It is a good habit to serve small and come back for seconds if they are wanted - this prevents waste and that urge you will have to say, "clean your plate". He has to try a bite of everything, but truly make it only a couple/three bites of everything.
Only if he has finished his plate does he get the dessert, pudding is an easy, fun dessert with lots of kinds. He can even help make it (spoon it into a fancy cup, top with whipped cream). He'll may be so eager to eat what he helped make, that he will eat his bites of everything and want his dessert right away. Explain that he has to wait for everyone to finish. While he is waiting, he might even have a couple more bites of various things. Make sure that you mention that you are looking forward to trying what he made.
He is also at an age that you MIGHT start letting him be able to help with dinner (little prep work like dumping what you measure out, getting things out of the 'frig, things like that). He can help set the table (if you don't trust him with the plates, let him at least put out the silverware, make sure he gets to tell dad AND positvie reinforcement is given).
Praise him for what he does eat, and don't nag about what he doesn't.
go back to his snacks in the afternoon. Little bellies fill up fast, but they also get hungry fast. Just make it good snacks and good foods, like raisins, grapes, orange sections or apple slices. If you throw in a little tiny cup of peanut butter and some crackers, he can make faces on the crackers with the fruit. Kids love that.
Before bed by about an hour and a half, give him another snack. This can be dry cereal (Applejack and Cheerios are really good), applesauce, peanut butter on toast, that kind of thing. Not a big portion, just something with milk to get him "through" the night. If he is not hungry, never force him to eat, but encourage a big cup of milk before he brushes his teeth.
I like the idea that you leave a few crackers for him. I would explain that they would be there for him, but NOT put them out until I was getting ready for bed, after he is asleep. That way he is not tempted to eat them while he is supposed to be going to sleep.
Your choice on the wrapping the dinner up to serve later. I am not a short order cook either, and do not want to make multiple meals, but I also remember/understand not liking what is made and not wanting it. If it is occasional, just make sure there is something he does like in every meal - preferably some form of fruit or vegetable.
If it is always that he doesn't like any of the stuff you make for dinner, try to get him more involved with picking out the groceries (fruit and vegetable department especially). Make it something exciting, asking if he thinks we ought to try this, holding it up. Fresh fruit and veggies are really bright, and they are exciting to look at, if you try to push that as opposed to the fancy packages of not so good food you can find.
Try to do fancy stuff with your fruits and veggies (take an egg slicer and use it on strawberries which is something he can help do, or julienne your carrots so they are cute sticks and not the big long carrot. Just different stuff like that.
How does he eat for breakfast? I am asking specifically if dinnertime is the only meal he is skimping on, and if that is so, why do you think this meal is such a hardship?
Honestly, kids go through lots of phases and you feel that you are a terrible mom for not getting the right nutrition in them, BUT if you are not giving candy and junk food, they are fine. All kids go through these spells.