Of the one's I've had, it doesn't matter much. The idea of widescreen format is a native format only, meaning, it may appear on the full screen, but stretched a bit...ie..Ninja Gaiden Black and the other one I have. It really doesn't make much difference.
The games that are not going to be sized great are the ports of shumps. Raiden series, Deathsmiles, ikaruga..etc..half of these games can be adjusted in the menu. If you enjoy a game, it doesn't matter much IMO. I have a harder time looking at Torchlight than
anything..that is annoying my eyes lately.