Your boy sounds a lot like mine! Although, while I don't say my DS is necessarily picky, he is selective. Semantics, I know!! I say he is not picky because he eats all fruits and many (most) vegetables, all different kinds of bread (we are in Germany so there are dozens of different breads of different colours and textures and he will eat most of them without questioning them), and all dairy products. Meats are a tougher one for him, he prefers processed meats (sausages, mortadella, frikadellen) or minced, such as turkey burgers or hamburgers. So I am not overly concerned about nutrition as he gets a good variety, but he does refuse a LOT.
He will also take one look at his dinner and just ask to walk away or not touch it. I say which part do you not like and he will just say "Not that one, not that one, not that one, not ALL of it..." even when there are many things that he DOES like...I am not sure what it is that prompts him to say that he doesn't like all of them though, we can't figure it out.
I know that the standard advice - not just here but everywhere - is to not make alternative meals for your LO, but I actually disagree with it in some regard. I have a child who WILL and who DOES starve himself out, and would prefer to hold off for 24-36 hours until there is something given that he likes. He will. And I can't do that. He is at kindergarten now (preschool) and they are given a hot meal at lunch and he did eat the first 2-3 days (I think it was not wanting to stand out as differnet) but now that he is settled he just does not eat. He doesn't like the food or the look of it or whatever it is, but he won't eat. And when I pick him up he is often crying that his tummy hurts and he is starving. Yesterday he cried the entire way home (25 minutes) because his tummy hurt and I had to make him some lunch when we got in. But then he did not like dinner either and was sobbing because he was hungry and did not like what I had made....how can you not make a child something else to eat in that situation? I refuse to allow him to cry from hunger when we have a fridge full of food that he does like!
I'm not meaning to criticize the advice of 'they must eat what you eat/don't make them a separate meal' because I do know where everyone is coming from with that,but I think that it is one thing to say it and another thing to live it iyswim. It's not as easy as people seem to think. When you have a child reduced to gasping for breaths through their tears over not liking what the food is in front of them, it is near impossible as a mother to say calmly "sorry but this is what is for dinner." No, what you do is have your own breakdown and wipe your own tears and then make them something that they want. And doing that is not copping-out or feeding-in to the problem or making it worse....it's making sure your children have food in their tummies. My son ate what we ate for a LONG time and just started getting fussier, so it's not like I started out this way. He ate xyz (name your crazy shocking food for a toddler to eat) many times and just got pickier. It happens, for whatever reason, and it has NOTHING to do with me having made him separate meals..that was not the cause of the problem, rather it developed as a survival tactic!!!!!!
I do try my hardest to make sure that every meal does include things he likes, but in that way it is still like making two meals, really. The other night I made homemade pizza - which he does not like but DH and I wanted pizza!! - and I cooked a couple of sausages for DS. I put everything on the table for him to select what he wanted and it was a mixture of things he liked and did not like...so really, it was a meal for us and a meal for him. And he selected the sausages, some beans and that was it. There is not much more I can do really - tell him that he needs to eat pizza or nothing and
he will choose to stay hungry with the tummy ache. :'(
One resource I have found helpful is a woman named Ellyn Satter - it was Deb in Oz who pointed me to her as she has been giving me such amazing support as I work through this stuff with my DS: Not sure if you know her (Deb in Oz that is!) but she has started discussing the topic on her own blog this week ..
http://www.homelifesimplified.com.au/beyond-feeding-fussy-eaters-fears-texture-issues-and-more/ Deb outlines her own experience with feeding her one daughter and she has been supporting me over the past couple of months in working through this to stop it before it gets worse with my DS, and in helping me with the emotional side of it as a mother as well. Anyway, it was Deb that pointed me to Ellyn Satter I don't love EVERYTHING she says but I did find that it helped me to keep a clear head and a clear focus about my DS's eating.
http://www.ellynsatter.com/the-picky-eater-i-43.html She does say not to make them separate meals, but one of the things she makes clear is that you need to make sure that you are putting foods out that they like. So you make pasta for dinner and your child does not like pasta, or it is a new food or you are just for whatever reason pretty sure he is not going to eat it. You need to make sure there are other things on the table for your child to choose from, and let him fill-up on the other things if that is the case. Her suggestion for this age is that there is a bread and butter basket as well and if your child chooses to eat 5 slices of bread for dinner and turn down the pasta, then that is fine. Put meals out buffet style and allow him to look at everything on the table and choose what he wants to eat and how much of it. Don't discuss with him what he has chosen or what he likes and does not like, don't comment on it, or put any pressure at all on him as to what he eats. Keep conversation around the table completely unrelated to the food. However, don't limit the food that is on the table to JUST things that your child DOES like. On nights that we have meals that I know DS loves (which has become rare as he has started refusing to eat spag bol/pasta with meat sauce which was a night when we knew he would stuff himself full...now he is refusing and insisting he does not like it...) but on nights like that I would stick a couple of things out and put them on the table to make sure there were other things to choose from....even if it was a plate with butter and a plate with butter mixed with parsley so that there was something new to choose from. I dump a few olives onto a plate, or some pickles...just so that the meal is not limited to things that he likes. If that makes sense.
A big thing with us - and I wish I had started this part sooner than 3yo - was NOT COMMENTING. My DH is horrible for it and tbh he has been since the day DS started on solids

but he is working hard as well. We say nothing about his food or what he is eating. No comments are made on how he gets it into his mouth or what kind of mess he makes or what he chooses to eat. There is a variety of foods on the table, take what you want and eat it how you want. Yes there has been a major regression in table manners for DS, but that is not important to me at this stage and are something that we will work on in the future...the eating is far more important IMO at this stage.
I think there is FAR more to it than 'just offer them your dinner and that's that' and not making separate meals.....I know that there is a basis to that advice but I have yet to find a single mother who can confidently say to me that they turned their picky eater around by just giving them food their child didn't like and eventually the child gave in and ate.