yes, my daughter is very picky about what she wears. she has no new clothes unless they were gifted to her - everything (besides socks and undies) she wears is hand me downs or thrift store purchases, so she has very few "outfits." however, now she's really into matching tops, bottoms, socks, etc. what i do is bring her several "outfits" and she has to choose from what i bring her. if she chooses only one item, say a dress or a shirt, it is up to her to go find something to go with it if she doesn't like my choices. if she dawdles, i tell her to choose within 3 seconds or i'll choose for her. it never reaches that point. so generally, she picks out her own clothes. there are certain rules, usually weather-related - no tanks without a long-sleeve underneath, no shorts without tights or pants or leggings underneath, always a sweater ("you can take it off when you get to where we're going"), no sandals without socks, you get the picture. although i'd love to be able to coordinate all her outfits (i hate pink!) she wears what she wants, as long as it's safe, modest and warm/cool enough. it has worked out quite well up to know (she's 3.5). oh, i forgot to mention, the clothes have to be CLEAN! if she wants to wear the same thing again and it's clearly dirty, she can wear it around the house, or sometimes i let her wear stuff in the bathtub.
in summary, part of your issue might be the "i pick your clothes today" thing. why not let him choose every day, with some very clear guidelines in place? unless there's an actual reason to choose his clothes, like you're going to church or a wedding/funeral (in which case he still chooses - just from a few outfits that you have pre-chosen FOR him), then let him decide what to wear. it's one of the few areas they can actually exert their control at this age.
and about the clothes that don't get worn, my daughter has things she didn't wear for over a year, but now that she wants to match, it has re-emerged. if you don't spend a bunch of money on clothes then it won't really matter whether he wears it or not.
good luck mama!