I actually did the opposite of you; when NiGHTS HD came out, I got it on PSN and played it, and just a few weeks ago I bought it on Steam cause it was on sale. And I played it all the way through again and life was good. I know what you mean though, after a long while of not picking it up, it still has that charm and magic that it did the very first time I played it. I even got my brother (who has been adamant for years on not playing due to thinking he wouldn't like it) to play it this time around too. And guess what. He DID like it. So HA.
I'm going to attempt to play it slightly more often than I have been. It's just a beautiful game all around.