I think Achievements are useful if they’re tracked separately by each save game. Minecraft does this, and I find it helpful when I return to a world save after a long time because I can use the achievements I unlocked to help remind me what I was doing and resume from there instead of looking at what clues may have been left behind.
That only works, though, if the achievements resemble game progress. Some games use achievements as entirely optional bonus challenges…
bananaghost