I think for me it’s Harvest Moon Friends of Mineral Town. Even though the triggers can be a bit bugged at times the achievements act as a great way to track progress like character events and your relationship level with people of the town. It’s not super hard to check when dealing with the bachelorettes because their heart level is shown but seeing exact percentages is nice.
They have also incentivised me to play a lot NES games I may not have normally played like Abadox.
I’m really interested in the Professor Oak Challenge subsets for the Pokemon games, but my favourite set I’ve seen was Kingdom Hearts: Chain of Memories [GBA], since it gives each boss a really good challenge achievement. Things like limiting the attacks you can do, types of attacks you can do, if you can move. It’s really interesting (and difficult!)