That isn't an argument; it's a non-sequitur. Whatever "better" means, it has almost nothing to do with market share. If it did, Dr. Dre would be "better" than Mozart. And he's not.
Yeah, but it is a very commonly held belief. For example, I talk to people who think that the Oscar nominations should only consist of the top box office hits, because for them, only what is popular could possibly be any good.
With Apple products it gets a little more complicated as, for example, people who want to see Apple products as appealing to rich snobs, an Android as a vindication of a more mass market approach.