I've been very frustrated trying to find unique ways to replay this game. I tried a "minimal green star" challenge and got as far as World 7, Bowser's Lava Lake Keep collecting only 5 or 6 green stars. But I got annoyed when I realized that to unlock Bowser's Lava Lake Keep, I'd have to go through all of the levels I just completed and collect most of the green stars in order to get deeper into the game. Which means that for every level you play, you pretty much need to collect as many green stars as you can, thus killing replay value.
The current challenge I came up with is a "no advanced power-up" challenge. You play the game as either normal sized or small sized, and you don't use any other power-ups. So no cat bell, no fire flower, no boomerang suit, etc. Also, no stage only power-ups like the double cherry or the propeller box. And no temporary power-ups like the invincibility star or mega mushroom. Only the regular mushroom is allowed. Also, you can't store any power-up in your item box except the mushroom.
Now try and collect as many green stars and stamps as you can. Now obviously, there will be some green stars and stamps that simply aren't collectible without the cat or the fire flower. But there are some that ARE reachable if you're clever.
The game is also harder now because you only get to survive one hit before you die, you don't have the cat power-up to climb past danger or the raccoon power-up to float past danger, and since you can't store any advanced power-ups in your item box, those rare always-a-mushroom power-ups that you probably ignored before suddenly become very precious.
It's been among my most replayed game because of local multiplayer. It's hard to not bring this game up when people come over. It's as addicting on couch multiplayer as Mario Kart 8. --- Have fun with whatever you like instead of telling people that they are having fun the wrong way. 3DS FC: 0748-3443-8121 (Safari: Panchan, Machoke, Riolu)
First time through I did everything as Mario, including collectables and flags (plus the rare levels where you must collect a stamp with other characters, and Champion's Road which I got rid of as all characters... didn't want to learn it again).
Since then, I've been using the other characters as an incentive for replays. I did Rosalina all levels today and it was a blast. Once they're all done, I'm sure the game's secrets will be fresh enough that I'll have a good time collecting everything again.
But I mean, to me it's like most games, I don't have to replay them the next week to find value in them. --- And this time!
I thought the game was decently replayable as single-player. LOTS of really, great levels.
Multiplayer replay is amazingly high. And maybe if it actually had online multiplayer then it would have been higher. Or maybe if it actually attempted to have extra content like the NSMB/SM64DS games had....
There are some really fun levels that I'll go back to and sometimes I'll try to get a good score/time. Most of the replay value comes from the multiplayer though. Playing solo is much different than playing with a second person. And that's different than playing with 3 or 4 people!
Even when I know everything about the game there's still surprises that come from multiplayer --- In case of a Zombie Apocalypse, follow me! 3DS FC: 2535-4356-9059 Name:Marcx