@ragingloli, I appreciate your question and don’t think it has an easy answer, or the question of what is art wouldn’t have been good for a lot of lively debate over the centuries.
But I don’t think effort and skill are the right criteria. I’ve seen things that took plenty of effort and that never would have come close to being what you’d call art. And I don’t just mean things that had no artistic intention. I mean that I’ve seen fellow students in an art class labor away for hours week after week on a project that from beginning to end lacked some fundamental aesthetic quality—in my opinion—that would even qualify it to be judged bad art. It wasn’t art at all.
And as for skill, I grant that some technical proficiency is necessary, but it isn’t sufficient. Skill makes for good craftsmanship, but that is not the essence of art. I would sooner grant the label of art to a sincere amateur effort with a strong aesthetic purpose behind it but a weakness in skill (which can be learned and increased with practice) than to a highly competent rendition of, let’s say, a seashore at sunset with splashing waves and two seagulls and an absolute vacuity with respect to artistic idea.
So I guess this means that I’m offering as my criteria (a) intention, (b) aesthetic purpose, (c) technique, and (d) artistic idea in addition to all those elusive components of beauty such as harmony, balance, contrast, emotional effect, personal vision, elevation of the spirit, and so on. I also tend to agree, but without a strong rationale, with those who think that utility takes a thing out of the class of art as such. Nonetheless, exceptions abound. And something can be made with great artistry and still not be what I would regard as art per se.
Your first selection certainly fits my idea of art, and your second doesn’t; but ultimately I can only qualify it as an idea of art that I find fitting. I can’t make a unilateral declaration about what they are or are not.