The Land Before Time (haven't seen the other one)
Piranha (original movie, not 3D) or Jaws 3
Definitely the original.

I found the remake better than the original, only actors I found good in the original were Ken Foree (Peter) and Tom Savini (Blades [machete biker]) Actually, except for Day of the Dead, I find all the Dead remakes better than the originals.
Out of curiousity, how do you find the original better? Me, I find the remake better because all but two of the actors were terrible, the plot was weak (compared to the remake), and I expected it would end the way it did. With the remake, everything that happened I didn't expect, and there wans't a single actor I found terrible.