I don't really like adapting games much. I'm not a system designer by either preference or practice – I like running and playing, and I really enjoy when the rules as written just… work. There's a joy in that.
I have, in the past, done a success-counting hack of Risus that I liked, an Approach-less version of Fate Accelerated where the Aspects have ratings you add to rolls, and I've done a couple genre re-skins for various apocalypse-engine games, including one for the kids where the whole system and character sheet fits on an index card. So… those. I guess. Fate's the easiest to hack, but I usually only run that for the kids, anymore.
Now, if you're talking 'adapting' like "use Monsterhearts, RAW, for a sort of Star Trekkie sci-fi game"… I'm slightly more down for that kind of mash-up fun. I've done adaptations of many, many games to the Amber setting, for example – some of them even worked.
(Either Urban Shadows or Masks would make fun Amber adaptations, for example, for different reasons.)