The sidebars probably appear because of how the TV decides to display the signal. It's a 480p signal, meaning not a lot of pixels, and generally to preserve picture quality a TV will by default just double scale the image. Since an HDTV has more than twice the resolution as 480p, this leaves some space left over.
I have this same issue with my 27" westinghouse, and I solved it by using a feature that allows me to cycle the picture through "standard-full-zoom."
standard just displays the ps2 screen with the default double-upscale and the black on the sides. Full stretches it out so the sides fill the screen but the image is out of proportion. But zoom hit the spot, it zooms up on the image until the entire screen is filled. With the ps2 display set to 16:9, this makes the ps2 image fit almost exactly.
(for some reason the ps2 image seems more like 16:10, so there's still a little black at the sides, but it's not a big issue)
A Sharp Aquos should have a similar zoom feature. Any good HD-ready TV should, in fact. Mine has it and it only cost $350 including shipping, and Aquos cost more than that.
If this doesn't work, add some extra details.
btw don't ps2 games look 10 times better in progressive scan? Huge difference.
>edit< it's not aspect ratio you want to tweak, you just want to blow up the image to the smallest possible size that fills the whole screen. Keep looking, there should be a way.
>edit< that's too bad that zoom doesn't work, Sharp oughtta be able to do better than my Westinghouse. But then again Sharp is a low-end brand too.
Is there a system info type of thing in the onscreen menu, where it tells you the resolution of the current image on the screen? If you look at it, and it says something like 576x384, or some similar low number, it's possible your sharp doesn't have the hardware to do the upconversion on its own.
This was an issue for people who connected their psp's to HDTV's back when it first became possible, some of them found that they just had a small box in the center of their HDTV screen, with the rest of it blank.
what's the exact model number of your aquos, maybe you could ask sharp what the deal is. I bet they have forums.
just so you know, ps3's upconvert ps2 games so this issue doesn't happen with backward compatible ps2's.