Wow. Yesterday was a good day. A really, really good day.
Before I go on about how, and why yesterday was so good, how's about we get to the RPGaDay Challenge question for today, hmm? OK, then...
Hmmm. This is another tough one.
A lot of RPG have covers that convey the proper feel for their respective games. Which is the best at it? I really can't say.
Rather, I can't think of one that stands out over any other. Some games whose covers capture their spirit well include:
Gamma World (2nd and 3rd Edition Editions)
Most Superhero Games
Star Trek (FASA)
Star Wars (WEG 1st Edition)
Tales from the Loop
Teenagers from Outer Space
and the majority of Japanese tabletop RPGs.
I like to think I did a decent job of that with my own game.
Which does it best? Sorry, I really don't have am opinion on that here. I can't think of one that wows me so much I'd dub it best.