Spelunky 2 enhances and expands on what worked in the first game without "fixing" anything that wasn't broken. In that way it's the perfect sequel for fans who have been playing this game for over a decade. Newcomers might be scared away by the difficulty and seemingly impenetrable secrets, but the effort to get through this is well rewarded.
There's no singular moment or element that stands out to make it an amazing experience, but looking back I'm quite happy that the game exists and that I got to play it. The story of Tyler and Alyson is worth experiencing and will live with you long after the credits roll.
If you loved every minute of Portal, The Witness, Obduction, or other sorts of puzzle adventures then Relicta does have something for you. But it's not as well polished as those titles, and doesn't offer as much creativity in puzzle solving, or variety in the puzzles themselves.