Big, fancy LCD and plasma TVs are just wonderful for 360 & PS3 games (well, most games). But for older games - and by old, we mean old - they're not so hot. And this is why.
This write-up by NFG (of the selectbutton forums) goes into astonishing detail on just why fixed-resolution displays aren't up to the job of displaying retro games the way they were meant to be displayed.
See, old cathode ray tube sets (ie your old TV) could handle the resizing of pixels - which is what your old 8-bit & 16-bit games were made of - just fine. But newer TVs need to digitally "fudge" the picture, and the way they go about fudging it results in a distorted, often ugly image. As you can see above.
Sure, this won't matter for 90% of you (who probably don't even notice anything wrong), but if this kind of thing gets your goat up, the full run-down is below.