Those replayable bosses in Tooie sure kept me busy back in the day. So did the multiplayer stuff because I had a few siblings to play with. I spent so much time in the Chao garden in the Sonic Adventures...but I loathed the grinding and replaying the same levels over and over again for items to raise them with.
Rayman Legends didn't give me much incentive to keep unlocking stuff. Once I beat all the worlds, the only reason to keep playing was to gather Lums and unlock character skins... They have the community challenges though, which are fine. The various time attacks and bonus levels were pretty cool. Super Mario Galaxy did that well, too. I wanted to keep playing even after beating Bowser. Any kind of added gameplay or challenge world is a plus in my book.
I think multiplayer races for Yooka-Laylee would be great. You compete against your local or online friends to see who can collects all the Playtonic medallion things, or fight a group of baddies, or co-op Portal 2 style.
you kuh lady