As usual, I already expected the answers about Shanks to be mostly negative here, because it's trendy to hate on Gary Tsu characters.
People don't understand that cliches aren't bad. Cliches are cliches because they work. Gary Tsu characters can work well if they are done well.
Shanks is the reason Luffy became a pirate, and he is the one he most looks up to, therefore it is fine for the story to treat Shanks like a Gary Tsu character.
A badly done Gary Tsu character is someone like Oden. He may have been cool when we saw him the first time, but eventually his character left a bad taste.
It's okay to like Shanks even if he is a Gary Tsu. It's okay to like Shanks even if he has a few panels of screentime. Quality over quantity. No one has presence similar to Shanks in the story.
But of course, let's go against the wishes of the writer, and let's hate the character he wants us to like, because that's so cool. And it's not even forced like with Oden was. Shanks doesn't have one single "strongest man" title or "worst criminal title".