it almost seems like it's rewarded in their games though is when I have a problem.  I think that part is unique with Nintendo games because only their franchises have been around for long enough for the reviewers to have grown up with them.  I don't think it's a SUPER significant portion, but it maybe inflated Mario Galaxy games from 92 meta or so to 97

Haha, nice twist there. I haven't seen much of Zelda Switch, but from what I have, it is indeed.

Not true as every sequel is a different scenario, each 3D Mario game has significant differences to the experiences, 64 is not like the Galaxy games and neither of these games are like 3D duo, the same can also be said of the Zelda games of all the 3D Zeldas only 2 of them are similar. Now compare that to your example of Ratchet and Clank where you can jump into any game in the series and the experience hasn't really changed despite what ever progressions they've added, fact is they do get criticized when something is the same as the NSMB series showed the reason you don't see that criticism geared towards them as often with most of their games is because the are significant changes to the experience from previous games.

It's pretty normal expansion on existing stuff when I play them.  Haven't really seen a revolution in Mario games since 64.  Ratchet and Clank has completely new guns, enemies, gadgets, and world themes while Mario keeps most of those things the same with goombas, jumping, fireballs and such.  You can point out similarities or differences depending on the narrative you wanna drive.

so Edge's review is up already on metacritic

just two more days for the rest

The is no similarity in the gaming experience of SM64 and Galaxy only the vague similarities that they are 3D mario game, the core experience differs significantly between the two games, when you add in 3DW which also has a different experience to it the series shows that it changes often, the concepts of these games differ in how the player plays through them. Adding new guns, enemies and gadgets to Ratchet doesn't change the experience in each installment, it may add some nice tricks but the gameplay experience doesn't really change from the previous games as the concept is still the same.

This is why Ratchet gets the criticisms while other games don't.

I don't know what you're talking about with "no similarity in the gaming experience" I played both and they play very similarly.  Enemies, art style, many power ups, jumping on things to kill them, the basic movements of Mario, collecting stars, etc. are all the same.

Again vague similarities, SM64 is open world exploration based where the player expresses themselves in how they play as they have more freedom as they're just dropped into a world and left to figure things out themselves, SMG is more linear and based around specific tasks with much less freedom and a more set way to play. A prime example of what I mean by vague similarities in your criticism is when you say Mario's basic movements, enemies etc... are the same when they aren't.

Mario's moveset in SM64 is way more vast where as SMG's is very simple, the power ups in the two games aren't even the same either as in SM64 Mario uses 3 specialized hats where as SMG was the first 3D Mario to use the traditional power ups. Enemies aren't the same save for 2, so when you say you've played both games I'll question what you actually remember from each game because I've played all 3D Marios and Ratchets and can see why reviewers have their views.

An example of another game that does what Mario does is Street Fighter where each game the player conducts their play different due to the different gaming experience generated from the change in approach. If all you focused on are the vague similarities between each incarnation like Ryu, Ken, Fireballs, fighting etc... then ofcourse you won't see the differences but when you do full on comparisons you realize why the games are different from the likes the Parry system to the Focus mechanics to even the V-System in SFV.

My gameplay experience vary just as much with Mario and Zelda as they do with ratchet and uncharted.  Both can be picked up fairly quickly and yet take time to master the nuance of in their respective gameplay.  Regardless of that I see nostalgic language used more In Nintendo reviews so I have to think that factors into their scores.  

Nostalgic language would be used more in their reviews because they've been around the longest of all the platform holders so obviously the language would be used to compare to previous games for longtime fans to know what direction the game has taken in regards to the rest of the series, doesn't mean that nostalgia has improved the score like you're arguing as in many cases nostalgia works against a game.