Well, I always admired 2xSaI on ZNES about 10 years ago. Then, when hq2x (and hq3x and hq4x) arrived I was amazed by the quality of its bright and crisp output. Of course it doesn't look like the original, but I found many games looked even better than originally thanks to having clear-cut, non-blocky diagonals without blur.
But I've just tried 50% and 25% scanlines and I'm beginning to see where the scanline-faction is coming from. With those quasi-scanlines (transparent scanlines) it looks really quite "genuine". Almost like back in the day with my Amiga 500 connected via RGB-cable to my RGB-capable TV...
Now here are eight more examples. Tell me which one do you like best:
1) Kreed's 2xSaI
(Double Pixels, then "Scale and Interpolate"):
5) 50% Scanlines without filtering
("Direct3D 16bit point filtering" in WinUAE to be exact)
6) 50% Scanlines with bilinear filtering
7) 25% Scanlines without filtering
8) 25% Scanlines with bilinear filtering
While with 100% scanlines the pic was far too dark, 50% and 25% scanlines do indeed look close to the real thing.