Please read my post before criticising it please.
I said if it has "2" or something in front f it, there is no debate about it being a sequel. For most games, the next game in the series is the sequel, such as Zelda games, but now there are so many diffent types of Mario game we can't say that any more. Does anybody really belive that Double Dash is a Mario 64 sequel? It's a Mario Kart sequel. Technically, all the games of the same genre are sequels to the one before it, but in Mario they are incredibly different. In my Oxford dictionary, it states that a sequel is "a published, broadcast or recorded work that continues the stoury or develops the theme of an earlier one.".