Mega Drive's higher resolution over SNES (320x224 pixels versus 256x224) doesn't make as much of a difference with games with digitized graphics (Mortal Kombat) because such games have "approximative" art unlike classic pixel art where you need precise graphics.

The Earthworm Jim games are a good example to show the massive advantage of the Mega Drive higher resolution because on SNES things went wrong in both games and each is a different scenario:
- Earthworm Jim 1 doesn't have redrawn visuals to adapt to SNES lower resolution and thus it has stretched (deformed) graphics with wrong aspect ratio once displayed in 4:3 and also smaller playfield (-20%). It's the worse and most common of the two scenarios.

- Earthworm Jim 2 on the other hand has some arts redrawn to keep things with a correct aspect ratio once in 4:3 but as consequence graphics looks worse, just compare both Earthworm Jim sprites on Mega Drive and SNES... It might be a more convenient scenario gameplay wise but it's still bad.

Funny enough, SNES fanboys always damage control when it comes to the resolution, pretending that it doesn't make a difference, that nobody sees it bla bla bla but LOL, it's the very first thing I noticed when I started playing on both the Mega Drive and SNES, about 2 years ago, so they can't be more wrong (or should I say, they can't be more delusional).