Fascinating thread. I guess the most likely candidates would be non-RPGish adventure games, but most of the ones I can think of are Tim Schafer's stuff, which is worthy replay just to enjoy the experience of it. For instance, if I had the time and it wasn't a technical nightmare to get running, I'd play Grim Fandango again in a heartbeat.
I suppose Sid Meier's Pirates! would be one. I beat it a few times, but I was just underwhelmed. It just didn't capture that same lightning-in-a-bottle that the original had. Too much gloss, not enough meat. It's still up on my shelf somewhere, but I haven't played it in years. Ditto for the Civ IV: Colonization add-on.
Portal. And if I ever get around to finishing it, probably Portal 2. Don't get me wrong, they're great games, but I don't really see replay value. And I don't do enough multiplayer to be likely to use that mode in P2.
And yeah, Borderlands -- once I've beaten the whole things with each character at least once. Because you do have to develop a whole different playstyle, especially in single-player.
LIMBO, once I finish.
And honestly, Space Pirates and Zombies. It's just not that interesting to me. I wanna beat it, just because. But after that, I probably won't bother with another playthrough.
In general, I play so many freeform strategy, sandbox-type games, or RPGish games, that there's usually replay value in there. And I'm notorious for not giving up on a game. Hell, I'm still trying to find a way for Birthright: The Gorgon's Alliance to somehow not suck. Because it was a really good idea...just...hellishly bad code and design.