New Super Mario Bros.
'New' really isn't a fitting word for the game; while there are indeed a few new things to the formula (see Giant Mushroom), the game feels and plays exactly like the old SMB adventures. So while it's nothing enticingly new, it is just the thing you enjoyed playing a decade or two ago, and still fun.
Before beating the game's final boss, you're only allowed to save after tower/castle levels, or at signposts blocking special paths by spending star coins (which are found in each stage of the game). This is rather inconvenient, and flies in the face of the DS's pick-up-and-play philosophy. However, the game really begins after you beat the final boss, and are then able to save at any point in the overworld. It makes going back to old stages and replaying them - to collect star coins, or to find new exits to unplayed stages - a real blast.
Progress: Complete