Except, a lot of those other fabulous eps have the same problem. OMWF, FFL, Restless - great TV, there's no denying, but context is a whole lot of the greatness. Restless, in particular - I can't fathom why anyone would show that to a n00b. It depends on four full years of previous TV plus foreshadowing for the next. OMWF certainly appeals intrinsically, but nothing has a lot of impact without the context of the rest of the season. FFL is fabulous enough on its own, I suppose, but part of why it hit me so hard the first time was the contrast with everything else I knew about Spike. I'd be really sad for anyone who saw that without knowing evil!Spike first.

Even The Gift and Becoming are culminations of season-long arcs, and that previous momentum is part of what makes them great.

(I have no idea why anyone would recommend CWDP to a newcomer, but I've never been as enamored of it as most folks.)

Now that I've been all cranky about people's choices, I'm trying to think what good intro eps are.

It turns out The Initiative is a pretty good intro. It's funny but not so much in the in-joke sense you're talking about, it's action-oriented, it's the main intro to three major season elements: Riley/Buffy, the Initiative, and Spike's chip. (I actually discovered this by sheer fortuosity: it's what I felt like watching the day the housemate offered to watch an episode.)