The only thing I look for in Mario games is old environments, items, etc. put to use in a new way, and if they can keep the geography of Mario's world connected in a way.
What I mean is, hearing old music, seeing ? blocks everywhere and old rolling hills with eyes is awesome. Take MK:DS for example! The SMB3 blocks and colored blocks with the screws or whatever made it and the Sun from that World 2 level!
Coming back to the locations of stuff.... I kind of don't like when the Mushroom Kingdom or the castle changes with every single game. Like with Mario Kart, Golf, and Tennis. Seeing the castle at every track with "Mario" or "peach" in it was annoying, like seeing a road going around the castle, then that same spot being home to Toadstool Tour's 18th hole on whatever the mario course was, then that same spot being home to the Mario & Luigi tennis courts. Then in SSBM the castle has water and rolling hills behind it, then with Paper Mario, Toad Town is right in front of the castle. I mean, crap, do they have Toad contractors that build whatever Peach or Mario want every year? I liked it in the first smash when the background to Mario's place was the castle as it appears in SM64, and in MK64, when the castle appears just as it is in 64 just with the track in front of it. That kinda tells you they were wanting to chill for a bit before going crazy. When are they gonna keep one thing or just modify the existing?
And also, a big question.. since you can see Mario's world in Galaxy... is it home to Nintendo's whole array of folks? Or are they living on different planets nearby that are near each other or visit earth for games such as brawl and the Olympic games? I mean, where in Mario's world is Delfino? Yoshi's island? Why in the world was Mario's world reduced to a chain of islands in SMRPG? Where is Toad Town, and Keelhaul Key and Rougetown in relation to everything else? Where's Mario's house and Luigi's Mansion? Where was the location of World 1's first level in SMB1? Was it next to SMB3's World 2? Standing from Vista Hill, can you see the Shine Gate in the distance?