Yo.  I'm a proud owner of the once elusive (now out of production of course) burgundy Nintendo DSiXL.  I still have plenty of games I have yet to finish on it, and I know both the 3DS and 2DS and backwards compatible with DS games.  Is there any signifigant difference in graphical quality when playing a DS game on a 3DS or 2DS?  Thanks.

I'm pretty sure the 2DS is just a flat 3DS, so I don't think so.

Should be no difference. There are no 3D effects when you play a DS game on a 3DS.

Some DS games don't work well on the 3DS (specially DSi focused games), but it's rare. Out of all my DS collection, only a Korg synthesizer and a Sudoku game didn't work on it.

Let be clarify by saying that I didn't expect the 3DS to display DS games in 3D. I didn't know whether or not the colors of a DS game might be more vibrant, stretched in horizontally or vertically, overscanned, etc...

Then there should be no problem. The 3DS screens are slightly bigger than the DS ones, so maybe you feel like the image is stretched somehow, but it's a minor thing.

The resolution is going to be a bit off cause it's stretched to fit the screen. However, you can (I think by holding starts as it loads) play the games in their original resolution while only using part of the screen.

DS games have never stretched for me. They always play in their original resolution, with a black bar on each side of the screen.

The bigger screens means theyre better than ever imo.

Enjoy playing those DS games, dont worry too much about it.

DS/DSi games on 3DS have a WORSE image quality than in the original hardware.
If you hold start+select at the launch it will run in native resolution with black bars and look much better, but also much smaller.

So, since you have the best device to play DS games (aka DSi), you will feel that you will get a worse experience even with the 3DS XL.

I would stick to a DSi for DS games.

Cheers