Taken to the logical extreme in Unleashed, unfortunately, which is a large part of why I didn't like that game.
I didn't even get halfway through Unleashed, I think. Got to the china place to start the next stage-
OH HEY DON'T HAVE ENOUGH SUN AND MOON MEDALS, GO FIND SOME MORESeriously, Sega?
Seriously? I have to search every inch of the hubs and replay the early levels several times over to unlock later ones? Unleashed's gameplay wasn't bad from what I managed to see, but it shames me that I never completed the damn game because of a collectables game mechanic that even
Sonic 06 wasn't stupid enough to do. I mean, yeah, Sonic 06 did force you to do a lot of the shitey missions and collect rings to buy crap you needed for the next levels, but otherwise it was fairly A-to-B; Unleashed skirts between A-to-B progression and forcing you to replay things repeatedly to get a bunch of hidden [parasitic bomb] so you can continue.
That's like playing Sonic Adventure 1 with Chao hidden in both hubs and stages, and having to find a certain amount of Chao to progress to the next stage by backtracking through the game to find them all. Then again, the Spyro games did the same technical thing, but only with the true final boss fights. Arrrggghhh