Perhaps you're over-thingking something simple?
The fact of the matter is that Ash just so happens to be one of the main characters therefore he will see all legendaries, partake in all sorts of world-ending-catastrophes, save the world, and just so happen to stop the utter destruction of all humanity blah, blah, blah...
The entire "Chosen One" scenario from the second movie was all because Melody picked him for the tradition her people have because of the legend. No where before, during and after the movie did it say anywhere that he was born to stop whatever apocalypse the world may face. It's more of a showing up at the wrong place at the right time situation. Again, this is because he is the main character and as you should all have noticed by now regardless of what book, movie, comic, poem, story, anime, cartoon whatever it is...the main character, almost, all of the time shows up to save the day.
Truth be told Ash shows up in a certain town, a certain disaster befalls the town and Ash saves the day. He's one of the good guys, the hero of the anime ergo he will step up and save the day and go on his merry way to whatever other place he feels like heading to.
And if he were to have recognition for saving the world countless times it would feed his ego, as it would anyone and everyone, but he has greatly matured as the anime progresses and like I said before he may let it get to him at some level but it's not like he's going to make everyone else bow to him. Hello!
And as for him lacking skills, sure, at the start of the anime most, if not all, of his badges were more of a...lucky fluke but over time he has shown great skills as a trainer. Yes, he will be beaten, after all, we're talking about your regular run-of-the-hill trainer not some sort of God. It just evens out. I love the character but I don't want to see him beat everyone. It's just to maintain a certain level of realism to it.
"Can't beat 'em all." after all.