This argument has gone back and forth for years. Look at the games and what the system is capable of. Later MD games would be really hard to visualize on the PCE. The PCE is really good at color and I think that is the systems strong suit. The md has poor color but can be displayed cleverly. Systems and chip sets have strengths and weaknesses. In my experience the PCE does shooters really well. The md certainly does animation better, and the snes did RPGs. It was an amazing time as all systems were so different and had so much personality. I don't think that the PCE suffered so much from it's "bit-ness" however it really does straddle the line between 8bit and 16bit. When push comes to shove you won't see earthworm Jim on the PCE or Ranger x, at least not without noticeable sacrifices.
And yet the MD/Genesis couldn't give you a decent copy of BomberMan, Fatal Fury 2, Fatal Fury Special, or Art of Fighting to save its own life. Dracula X is far better then Bloodlines hoped to be, visually or otherwise. Snatcher, better looking on PCE. Raiden, better on PCE. This happens to be the case with most games, including all the arcade ports, that were on both systems, and there are plenty of games on PCE that are visually more appealing then Ranger X. Ranger X is mostly standard fare for the Genesis in its later life, with a few neat tricks in spots but honestly a lot of smaller to average sprites, dull looking colors and boring enemies and sub par audio. It's also another one of those titles that could have been done on on PCE, esp if on Super Cd. Yeah you'd lose the background scrolling, but f*ck it, who cares. The sprites and over all detail and color in the game could have been improved, and over all that is more important.
The Genesis was a great system for being able to move a lot of stuff around the screen fast background wise. Regardless of that, a lot of the crap did not look that great as a whole. Low colors and a rough look are common among even the top tier Genesis titles, and Earthworm Jim is def not that impressive. Tiny to average sprites and a lot of filler spaces in the background art where there is no actual details. Other then the scrolling going on in the background, the game could have been done on PCE, with cleaner, better looking sprites for that matter. The sprite animation could have been handled fine. If you are going to name a game that really holds its own still on the Genesis, pick something like Lightning Force, Shinobi III or Sonic 2, but def not Ranger X or Earthworm Jim.
I'm not really going to go into the sound, people have their own preferences on that, and both systems are able to generate great music and voices when the right programmers are handling it. In the end though don't just assume that because it wasn't done on PCE that it simply can't be done. You may have to ditch some background scrolling, sure, but that is not what makes the game fun or over all visually appealing (and push come to shove, the PCE does have its own nifty tricks up its sleeve, see Vasteel or Metamor Jupiter for a couple of examples). Most everything else the PCE does better, hands down. And back onto Earthworm for a sec, the only reason Earthworm Jim didn't even get a TG16 release was because Interplay/Shiney did not support Nec systems.