This thread is a bit much for me, there are so many games I've played retroactively and loved. I think the main one would be the Metroid series just in general. I'd never played a Metroid game before 2014, then went on to play most of the franchise. Super, Fusion, Zero Mission, Prime 1, 2, 3, all apply here.
Other than that... Okami... Many Zelda games (though some are still overhyped anyway). Think that's about it, really. The list can get really long if we start talking about games I've played 1-2 years post-release, but I'm going with longer term stuff here.