I used to feed him Royal Canine for his age (maxi junior), but all of a sudden he would not even touch that or any other dog food. He does eat any home food we would give him. Yet, we are not at all happy with what Happy (our dog's name) would eat.

So there are lots of things that can cause a dog to stop eating, sickness being one of them. Is he not eating completley,or has he just drastically cut back?

Is he drinking water? What do his stooles look like? Has been into anything that could make his tummy upset? Bones, garbage,etc...
Is he up to date on vaccines?
Is he exhibiting any other symptoms?

If he is quite happily eating human food then I'd say he is just going through the fussy stage.
Most dogs go through it... usually at around 12 months but sometimes earlier.

Of coarse a full vet examination is needed to make sure there is nothing physically wrong with your dog but I can tell you I went through a very similar thing with one of mine.
He just flat out refused to eat for about 3-4 months. He was a bag of bones, so much so I was embarrassed to take him out of the house. I tried feeding him a whole buffet of different foods but he wouldn't touch any of them.
Eventually I just kept feeding the same food every night, if he didn't eat it the bowl got picked up until the next day.
He started eating finally and he is now actually rather chubby and needs to go on a diet!