I hate when someone says: "I had the same idea 5 years ago, but back then I thought it was lame. Or I was lazy. Or uninspired. Now someone else has done it and it's hot as shit on a stick. But I thought of it first so this thing NOW is a pale imitation of this thing THEN that never was."
It's like comparing apples to... the thinking of an apple. Well, I mean thinking about an apple. Until it is an apple it doesn't exist. Thoughts are fleeting and for the most part private.
It's the person claiming credit for a screenplay of a box office smash that was never submitted but he had the idea first but never showed anyone.
Someone else striking gold on a claim that you investigated but you never bothered to claim and being bitter about it is just... sad.