I don't know, while I used to get kind of picky about which character sheet I used, I have also spent years using some of the plainest, most perfunctory character sheets ever made. Just as an example:
It's just dull dull dull but that's what we used a lot, I think for AD&D 2E.
The basic sheets that came with AD&D (1st edition) had more flair than that.
The last few years though I think Savage Worlds has the coolest character sheets. Here's Deadlands Reloaded - it's probably my favorite right now:
Here's Necessary Evil:
Here's the sheet for Slipstream, the retro pulp sci-fi setting:
Here's Weird War 2:
I like these a lot and think they add to the atmosphere when you're getting a campaign off the ground. Considering they are usually juts a front and back print job I'm willing to burn up some ink for a nice-looking sheet.