Are you sure it's the ideas that you stop liking after a day or two, or is it possible that you just aren't crazy about the actual work of writing? For me, it's a lot more fun to brainstorm and come up with all the concepts and characters, and then it's work (rewarding, but a more delayed reward) to discipline myself to write it all down.
Oh no, I love actually writing and putting down my ideas on paper/word file, and I enjoy writing scenes (as terrible as they might be).
My only problem is that I get fairly excited about an idea for about a day or so, and though I sometimes write it down and brainstorm a bit, I still get bored after a short while, and have to wait until I think up another idea.
As for the other advice, I'll take all of that advice. I'll try and polish my, uh, literary turds as PrincessofPersia said, for one thing.
Writing similar to an author whose work I like may be a problem, because I have a pathological fear of being accused of plagiarism. I don't want to be accused of stealing ideas, even if that idea is removed far enough from the original mimicry, and won't see the light of day in any case.
I do like the concept of watching/reading something I consider terrible and taking it as a challenge to write a similar, but better story, thanks for that.
I don't think my first ideas are gold, but I do want to get them as correct as possible the first time, which is part of why I'm hesitant to write.
As for idea generation, the real problem is that I get loads of ideas in a short period of time, but I'm usually far enough away from any writing tool that I don't remember half of them, and I get bored with the ones I do recall.
And yeah, the internet is both my best friend and worst enemy. Perhaps I should shove off and do a bunch of random writing on the tool I know doesn't have the internet.
I'll try doing writing prompts and random brainstorming, thanks for alerting me to that.
All in all, thanks for the advice, everyone.