SML1 - the sprites are tiny,jumping feels weird (like you are playing on mars gravity) but otherwise it's a decent game,some stage are shooters which is pretty weird for a mario game,it also features some kickass bonus music
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SML2 - i like it a lot,the levels are pretty weird,there is a giant house where you fight ants,a horror themed pumpkin,a sunken ship,a giant robo mario and at a certain point you float to the moon inside a giant bubble,it's kind of an underated game if you ask me
Wario Land - not as crazy as super mario land 2,and feels a little slow compared to mario but it features lot of hidden secret and stuff and kickass music
Wario Land 3 - this one is pretty peculiar for two reason,the first is that you can't die whatsoever,instead when an enemy hits you,you get inflicted by a status which usualy force you to go back for a reason or other,for example you might encounter a zombie enemy and if you get hit by it,you turn into a zombie but zombie can't jump so you need to go back to unzombie yourself,or one of the enemy hits you and force wario to turn into a spring which automaticaly make him jump inside the exit,it's quite unique and sometimes you are forced to get hit yourself to go trough the level
the second thing that makes the game unique is that there is no order to the level,each level has 4 items and each item just open a new section of level,like you might encounter a owl in level 3,4 and 6 but he does nothing but after you find the sun,the owl awake and now you can ride him to find new stuff,it's not exactly like metroid but it's still pretty cool