ohh, man, how can you do this to me? my favorite disney movie versus a staple of my childhood? i just...can't...choose...arg!
*flips a coin*
wizard of oz it is. but not out of any lack of love for the lion king.
EDIT: forgot to add suggestions for future movies:
the star wars trilogy (one by one)
the sound of music
willy wonka and the chocolate factory
mary poppins
the land before time
an american tail
how the grinch stole christmas
charlotte's web
babe
nightmare before christmas
any muppet movie
all dogs go to heaven
the princess bride
any disney animated classic, such as snow white, cinderella, dumbo, etc. you could prolly do several months on disney classics alone. i could go nuts, trying to list them all.
think classic kids movies, since so many people on these forums are pretty young and will have seen them, and the older people will have usually grown up with them.
i think you'd be safe doing the harry potter movies, pirates of the caribbean, and shrek, too.
you might want to also think about:
forrest gump
the godfather movies
the batman movies
casablanca
jaws
it's a wonderful life
singin' in the rain
terminator
grease
gone with the wind
all considered classic, but i'm not sure how many would have been seen by members of this particular forum.
you could put a list of upcoming movies in your first post of every poll and ask people if they've seen most of them.