I know that fancy new stuff is coming out every day, and I sure haven't seen every system on every display with every upscaler but...I'm pretty sure most of the HDTV guys haven't seen the best SD has to offer either. From my experience, SD stuff really does look best in SD.
I know there are guys that are totally happy with their giant ass overly sharp zero dot pitch million candle power billboards, but I've never seen one that looks as good as, say, a 17" PVM bought off Craigslist for $50. The stuff is just not supposed to be that huge, and it's definitely supposed to have scanlines.