The difference here is that there is nothing about the handheld versions that make them good fits for the system, they're just dumbed down versions with less content than the console/PC versions. Maybe they'll have minigames or a tacked-on feature or two to make use of the touch screen, but those are rarely ever good.
People want games that are a good fit for handhelds, which the LEGO games are. Smallish sized levels and a focus on unlockables and replayability make them the perfect pick-up and play handheld games.
If the developers put some effort into the handheld versions and make them good, unique experiences tailored perfectly for their specific handheld, I'm sure we'd all be thrilled! But as that's probably not going to happen the best we can ask for are decent ports of the console versions.