I love Land Before Time the most, then An American Tail and finally All Dogs go to Heaven.
I enjoy Pebble and the Penguin and Rock-a-Doodle though more when I was younger, now i'm older I see quite a few flaws in both. I also quite like Titan A.E., though I feel it had more potential.
I never played the games, though i've heard their good, and i've never seen Anastasia, Secret of NIMH or Thumbelina.
I will add that Don Bluth didn't work on Fievel Goes West, nor any sequel or spin-off of any of his work except Dragons Lair 2 and Anastasia: Bartok the Magnificent. I will say that out of all the sequels and spin-offs i've seen, Fievel Goes West is the best (most likely because it was the only to see a theatre release).
I also see you have not mentioned A Troll in Central . OK OK I wont mention it.

There's not "All of the Above". So I voted Land before time, although I love them all.

The Secret of Nimh is love<3333333
I watched that when I was young then watched it again and it's still just as good. ;w;

OMG! The Land Before Time! Not too many movies that I watched as much as that...

I remember being scared of the SHARPTOOTH the first few times I saw it. It's a T-Rex with an appetite for baby dinosaurs! It seemed so evil and scary back then, lol.

I've never felt so lost... I have no idea what to do at this crossroad.