I think most good Sci-Fi requires the technology and setting to be significantly different than our own and I just never felt like the world they were living in was really any different than the one I'm living in.
That may be *your* definition of Sci-Fi, but it certainly is not everyone's. And as someone else mentioned, "Eternal..." won Sci-Fi awards.
To me, "Sci-Fi" is most easily boiled down to
"What-if?" technological scenarios - and how they would affect us:
- What if time travel was possible.
- What if we had warp drive.
- What if we were able to travel between parallel realities.
- What if we had technology to control our dreams.
- What if we had the technology to alter memories.
- What if... Well, you get the idea.
Many Sci-Fi films or series combine several of those. Some do not. But to narrow yourself to films set in the future or films that have aliens (or whatever your definition might be) is selling the concept short, I think.
Sci-Fi, like any other story telling category, is are ultimately about characters. (good stories, anyway)

Good Sci-Fi tries to examine how these technological changes/abilities affect the characters. Which is something "Eternal Sunshine of the Spotless Mind" does in a great way.