A 2d Mario RPG would be well accepted because it would be fleshing out more of the 2d Mario experience (instead of ‘changing’ the experience). Remember that Zelda 2 was seen as a successor and was very well accepted. Today, in the future, people don’t understand Zelda 2 because they defined Zelda 1 as a ‘top down game’ and Zelda 2 seems ‘different’. But if you defined Zelda as the Nintendo Fun Club Newsletter did as an ‘arcade/CRPG’ hybrid, then Zelda 2 is a more faithful sequel to Zelda 1 than Link to the Past.
To throw a monkey wrench into the discussion, Mega Man X was a good successor for Mega Man in ‘next gen’ (SNES) than Mega Man 7. Why is that? Mega Man X wasn’t really a different game. But Mega Man X was like a fresh start from all the tired cliches that were beginning to add up with the Mega Man games. Mega Man X was to Mega Man in a way like how Star Trek: The Next Generation was to the original Star Trek.
A new generation of kids grew up with Mega Man. The veteran Mega Man players even found Mega Man X interesting since it was placed in ‘the future’ of whatever time period Mega Man Classic was. The continuity was very important to bridging the old customers and the brand new ones. The message was clear: this wasn’t your older brother’s Mega Man.
Thinking of the Star Trek, the series went on for 40 years (!). What tied it all together was a sense of continuity (e.g. McCoy appearing on the first episode of TNG as an old man, Scotty appearing in the episode ‘Relics’, etc.). Even if something new is done, a sense of continuity is well appreciated.
Zelda II’s continuity was very strong with Zelda I. Link to the Past was seen as a pre-quel and began to get confusing. Link’s Adventure was all a dream (as was Doki doki Panic). All the crazy ideas of time lines began with Ocarina. But why did fans obsess over the timelines? Because they were looking for continuity to tie everything together.
Super Mario Brothers even had continuity of a sort. In Mario Brothers, Mario and Luigi are not yet in Mushroom Land. They appear to be cleaning out the sewers where strange monsters emerge. Apparently, they entered those pipes and ended up in Mushroom Land in Super Mario Brothers. After SMB 1, SMB 3 was a more detailed romp through Mushroom Land. And Super Mario World appeared as if Mario and Luigi pursued the retreating Koopa Family into Dinosaur Land. The Ghost Ship has to be a crashed doomship from Super Mario Brothers 3.
Gamers do like some sense of continuity even if it is a very, very basic frame. Metroid did this well until Sakamoto appeared with Metroid Fusion, Metroid Zero Mission, and Metroid: Other M. Samus goes to Pirate World and destroys Mother Brain. Then Samus goes to SR388 and wipes out all the Metroids except a baby. The pirates return back to their world after stealing the baby Metroid to make new Metroids. Samus then wipes everything out. But Metroid Prime showed continuity can still continue. Sakamoto took the story too seriously.
Blizzard games provide a continuity through all of them. Currently, gamers hate where Blizzard is going with these stories but they are there. Starcraft 2 isn’t a complete remake of Starcraft 1. It continues where Starcraft 1 ended. The same for Warcraft 3 continuing where Warcraft 2 left off. The WoW expansions sell because they continue the continuity of the Warcraft Universe. People buy it to see the universe fleshed out more.