platformers are defined by mechanics wherein you control a character in a certain fashion to traverse stages; every Mario game has not only significant differences in control because of the addition and/or removal of power-ups, but also unique stages compared to every other Mario game
the difference between saying that Call of Duty arguably being the same every time and saying that Mario games arguably being the same every time is that
Call of Duty and etc. actually reuse the same mechanics in each game, and there are next-to no distinguishable differences from game to game other than the addition of new weapons which function the same way as previous weapons
whereas a Mario game that is basically the same as a previous Mario game is, by virtue of Mario games being platformers, literally impossible from a design perspective
comparing two Mario games and saying that they're basically the same is more or less synonymous with saying "hey I don't know anything about video game design", whereas the difference between Call of Duty 12 and Call of Duty 13 are more akin to the difference between Super Mario Bros. and the version of Super Mario Bros. included in Super Mario All Stars; different in a visual capacity, maybe fixed up a bit coding wise, but is otherwise the same damn game