If I may jump in: Fallen Idols, Curious Case, Real Ghostbusters, Sam Interrupted, Swap Meat, and Dead Men are monster-of-the-week episodes, though there are bits in all of them that tie back to the mytharc. I Believe looks like it's supposed to be a mytharc episode, but unless the guest star makes a return appearance (and I've seen no spoilers indicating that he will, which does not, of course, mean he won't), I'd file it with non-mytharc. 99 Problems is a monster-of-the-week but it has entirely too many mytharc-significant bits to be skippable. Everything else is a must-watch.

Quality-wise, Fallen Idols was meh, don't think too hard about the mechanics of I Believe, if you found Monster At and/or the Becky bits of Sympathy painful then you really don't want to watch Real Ghostbusters, Sam Interrupted was meh, Swap Meat was a seriously wasted opportunity, and 99 Problems and Hammer between them have ninety-nine problems with sexism, racism, ethnocentrism, and not doing the research (though Hammer's leading lady is awesome till her last couple scenes and two of the other guest stars also rock hardcore). Everything else is a must-watch.