Personally, I highly doubt that Mario Galaxy, Twilight Princess or Metroid Prime 3 are any easier than previous games in the series ...
I know a few gamers (who have been playing games for longer than many posters on this site have been alive) that the Wii is their very first Nintendo system since the NES or SNES and they have all (seemed to) struggle with one of these games. One thing I do know is that there are certain design elements which gamers can (and do) becomed accustomed to, and if the gamer is experienced enough with these series the games will consistently seem easier and easier; this is actually true of most series, but there are few game series that have existed for 20+ years and had the same designers impacting the design for all that time.
