He is, generally speaking. He lacks that street style Mario has though.
As for Young Link vs. Link, Link kills easier and has better survivability. Young Link is more mobile though, which counts for a lot seeing as how Link is very sluggish and pretty slow. I've seen a lot of arguments for which of the two is actually more viable. I think Young Link has more relevant specific match ups for tournament (YL/Puff for one), but Link is just a better overall character.
You're not the only one who likes Roy more than Marth by a longshot though. But Roy is not nearly as viable competitively.
EDIT: I don't think Doc is objectively better than Mario. Mario feels a bit quicker, and his jab combo is much faster. Plus his cape recovery is much better. It's not enough to make up for Doc's strengths overall, but it's enough to not count him out. I play both. Mario is just #thecoolest but sometimes in tournament you need the Medicine Man.