Like Jason said there weren't any intentions to create a sequel at first (I think LBT 2 was released in 1994).
As for the question, I'm afraid it really needs to be pinpointed a bit more, as it is difficult to decide what is included in the term "like the original" and what is not. Are we talking about the animation? The plot? The whatever?
As for the animation, I doubt that a purple sharptooth (LBT 2) would have been admitted to a "more like the original" movie, not to mention the shrill colored ophtalmosaurus in LBT 9. There were often softer colors, less sharp borders and more spectacular perspectives in the original movie. It might be, that keeping this up in the sequels would have been an improvement. However, I can't say I was very disturbed about the sequels' animation unless it comes to some elements in later movies, namely "confusion of colors" (green lava in LBT 7, deep green skies in LBT 8, turning red of everything in case of danger (LBT 5, 6, 10), exaggerated use of color to indicate temperature LBT 8), and exaggerated 3D and photorealistic effect that don't seem to fit to the normaly drawn characters in LBT 10.
As for the plots, there are a number of things that I don't think would have been tolerated in movies more like the original. We don't need to go as far as looking at the movies that are clearly in conflict with the original to find examples.
To begin with, the first movie seemed to show (never said so explicitely though) the Great Valley was the last green spot in a vast wasteland. In the sequels the Valley has partly been "disenchanted", most likely because it turned out impossible to limit all stories within the walls of the Great Valley.
Also, I don't think a friendship with a sharptooth would have been tolerated, at least not the easy way it was established in LBT 2, in a movie more strictly based on the original.
Finally the friendship between Littlefoot and the others was something extremely special in the original movie in which the racism among the various kinds could be felt very strongly. In the sequels it is hardly something special at all (with LBT 4 being a remarkable exception as it seems to limit the lack of racism on the Great Valley).