In recent years...
Mario Kart 8 was great. 50% extra game for 12 bucks... amazing deal.
Bloodborne: The Old Hunters was a great expansion worth every penny.
Shovel Knight is like... unreal. They didn't need to give us so much... but they did anyway.
Donkey Kong Adventure in Mario + Rabbids was an insanely good expansion
Torna: The Golden Country is pretty much a full on game disguised as a DLC expansion. And in some aspects it's even better than the main adventure. Also, we got a ton of new content for the base game
Splatoon and Splatoon 2 spent years giving people free updates with weapons, maps, game modes, events and more. And Splatoon 2 got a nice (paid) story expansion
That's the good. The bad...
Both Smash Bros. Ultimate and Smash Bros. 4 have awful DLC. I don't care how much it costs to make new characters and stages. 25 dolars for a 6,6% increase in overall content is ridiculous. And Smash 4 was even worse, with the pack with all characters costing 35 dolars. 35. Wow.
Zelda Breath of the Wild Expansion Pass was not bad in terms of content. But it is bad to lie to people. They promised "a new original story". I don't know what Nintendo understands by that... but what we got was not a new original story. And I'm very disappointed with Nintendo for that.
Pokémon Sword and Shield Expansion Pass will be massively disappointing as well. I know, I'm saying things I can't prove yet. And if I'm wrong I will eat my words, I promise. But I strongly believe that they will give people like... a few hours worth of content. Like... twice the Delta Episode duration at best. And then all what will be left is catching the new Pokémon and go back to the competitive aspect of the game. All for 30 bucks. And then people will miss a well made third version (not like US/UM).